The concept is central to acceptance and commitment therapy (ACT) and explains why very different behaviours respond to the same intervention.
An unpleasant thought or emotion appears. You do something so as not to feel it: avoid the situation, check, postpone, drink, eat, open your phone. The discomfort drops immediately — and that is exactly the trap, because fast relief reinforces the behaviour far more strongly than any consequence three months out.
The cost is that life narrows around the avoidance. You stop going to events, stop starting projects, stop saying what you have to say. Each avoidance buys short-term calm with long-term territory.
ACT names the alternative psychological flexibility: the capacity to make room for discomfort and act anyway, in the direction that matters.