The above quotes are from 'The Feeling Good Handbook'. The next few will be from the book before that one, by the same author, simply called 'Feeling Good'. The Handbook was a sequal written later.
From 'Feeling Good' David Burns
(page 92)
Coercion and resentment. A deadly enemy of motivation is a sense of coercion. You feel under intense pressure to perform - generated from within and without. This happens when you try to motivate yourself with moralistic 'shoulds' and 'oughts'. You tell yourself, " I should do this" and " I have to do that". Then you feel obliged, burdened, tense, resentful, and guilty. You feel like a delinquent child under the discipline of a tyrannical probation officer. Every task becomes colored with such unpleasantness that you can't stand to face it. Then as you procrastinate, you condemn yourself as a lazy, no-good bum. This further drains your energies.