Lesson 3: Turning “I Must” Into a Belief You Can Examine

Lesson 2 showed how one situation can be interpreted in several ways. This lesson looks at a kind of thinking that often sits underneath anxious interpretations: rigid demands, the “musts,” “shoulds” and “have tos” we place on ourselves, other people and the world. The aim is to take a demand that feels like a fact and turn it into a belief you can look at.

Module: 3, Understanding thinking

Learning objective

By the end of this lesson, you should be able to recognise a rigid demand, restate it as a belief, and compare it with a more flexible alternative. You’ll also see how three related therapy approaches handle demands differently, and what the evidence says about each.

The concept: demands and preferences

Many anxious thoughts contain a hidden rule. “What if I mess up the presentation?” becomes far more distressing when it rests on “I must not mess up.” The prediction is about the future; the demand is about what is allowed to happen.

Rational emotive behaviour therapy (REBT), introduced by Albert Ellis in the late 1950s and described as one of the main pillars of cognitive behavioural therapy [1], gives this idea a central place. In REBT, a rigid demand is a belief that something absolutely must or must not happen: “I must be liked by everyone,” “I must never make a mistake,” “Things must go to plan.” It contrasts with a flexible preference: “I’d really like to be liked, but it isn’t essential,” or “I want to avoid mistakes, and I’ll still make some.”

REBT theory proposes that rigid demands bring other beliefs with them:

• Awfulising (also called catastrophising): that it would be awful, the worst thing possible, if the demand weren’t met.
• Low frustration tolerance: that you couldn’t stand it.
• Depreciation: that falling short would make you, or someone else, a failure as a whole person.

There is some direct support for that structure. In a study of 313 trauma-exposed military and law-enforcement personnel, demandingness beliefs were linked to post-traumatic stress symptoms through catastrophising, low frustration tolerance and depreciation beliefs, as REBT predicts [2]. It was a single cross-sectional study about trauma, so it shows a pattern of associations rather than a sequence of causes. More broadly, a meta-analysis of 100 samples found irrational beliefs moderately associated with distress, including anxiety, depression, anger and guilt (r = 0.38) [3]. That is a correlation; it doesn’t show that the beliefs come first.

How CBT sees the same “must”

Beck’s cognitive model, which underlies much of CBT, also includes rules among the beliefs that shape how people respond [4]. In CBT these are often called rules for living or assumptions, frequently in an “if… then…” form: “If I make a mistake, people will think less of me.” CBT tends to treat them as predictions that can be checked against evidence or tested in practice. REBT focuses more directly on the “must” itself and whether it holds up. The two overlap a great deal but aren’t identical, and practitioners within each vary.

Perfectionism is a good example of where these ideas meet. CBT programmes for perfectionism work on exactly this kind of rigid standard. A meta-analysis of 15 randomised trials (912 participants, mostly young adults) found large reductions in concern over mistakes (g = 0.89) and a small-to-medium reduction in anxiety symptoms (g = 0.42), although few trials compared it with another active treatment [5].

What the evidence says about REBT

A 2018 meta-analysis covering 50 years of REBT research included 84 articles. Compared with other interventions, REBT had a medium effect on outcomes (d = 0.58) and on irrational beliefs (d = 0.70) at the end of treatment [1]. The authors concluded REBT is a sound intervention but outlined limitations in the existing studies. Those results cover REBT in general rather than anxiety disorders specifically, so they are moderate evidence for the approach, not a verdict on any one condition.

A worked example

The following is a fictional example used for teaching.

Jordan has been asked to give a short toast at a friend’s wedding, and has felt sick about it for weeks.

Step 1: Find the demand. Asked what worries him, Jordan first says, “I might forget what to say.” Asked what would be so bad about that, he says, “I have to get this right. It’s her wedding.”

Step 2: Write it as a belief. Putting it into words makes it visible: “I believe I must give a flawless toast, and if I don’t, it would be awful and mean I’ve let her down.”

Step 3: Examine it. Three questions are often used, each from a different angle:

• Does it fit how things actually are? No rule says the toast must be flawless. Plenty of wedding toasts include a stumble, and the weddings carry on.
• Does it follow logically? Wanting something very much to go well doesn’t mean it therefore must.
• Is it helping? Jordan notices the demand makes him avoid practising, because practice reminds him of the pressure.

Step 4: Write a flexible alternative. “I really want the toast to go well, and I’ll prepare for it. It doesn’t have to be flawless. If I stumble, that would be uncomfortable, but I could cope, and it wouldn’t mean I’d let her down.”

Jordan’s goal isn’t to stop caring. It’s to keep the care while loosening the demand.

Common misunderstandings

“Every ‘should’ is a problem.” Many shoulds are practical shorthand. “I should leave by eight to catch the train” really means if I want that train, then I’d better leave by eight. The ones worth examining are absolute and non-negotiable, especially when breaking them feels catastrophic.

“A preference is a weak version of a demand.” Preferences can be very strong. “I’d strongly prefer not to be rejected” is a full, honest feeling; it simply leaves room for reality.

“Examining the belief is the only option.” Acceptance-based approaches offer another angle. Rather than debating whether the demand is true, you might notice “I’m having the thought that I must get this right” and choose how to act anyway. This isn’t a fringe alternative. A meta-analysis of 39 randomised trials of acceptance and commitment therapy (ACT), with 1,821 patients, found it outperformed control conditions (g = 0.57) and found no significant difference from established CBT [6]. In a direct trial with 128 adults with anxiety disorders, CBT and ACT improved similarly by the end of treatment; both included exposure to feared situations. Over the following year the picture was mixed, with ACT ahead on clinician-rated severity among people who completed treatment and CBT ahead on quality of life [7]. Module 6 explores this approach.

Optional reflection

Think of something you’re anxious about at the moment. Is there a “must” hiding inside it? If so, try writing it as a belief, then as a flexible preference, and notice whether the two versions feel different. You might also try the acceptance version: “I notice I’m having the thought that I must…”

When to get support. If demands like these feel deeply entrenched, are tied to painful experiences, or sit alongside low mood, disordered eating or exhaustion from working to impossible standards, a qualified therapist can help you work through them; a GP is a good first step. If you are in crisis or having thoughts of harming yourself, contact emergency services or a crisis line now: in the UK and Ireland, Samaritans on 116 123; in the US, call or text 988.

Recap

• Rigid demands are absolute “musts” and “shoulds” that often sit beneath anxious thoughts.
• Writing a demand as a belief turns it into something you can examine.
• REBT targets the demand itself; CBT often treats rules as predictions to test; acceptance approaches focus on your relationship with the thought.
• Irrational beliefs are moderately linked with distress, and REBT, CBT and ACT all have trial evidence, of differing size and quality.
• A flexible preference keeps what you care about while leaving room for reality.

Previous lesson: Lesson 2: One Situation, Several Different Interpretations