I flake on plans a lot. Most of the time I get brow-beaten by a more persuasive person to promise myself to plans that I would really never see myself going through with. I have an inability to say no and be firm about it, and people usually jump in at the point of weakness and firm up a plan for me. And then I mull over it (worry about it) till I call and apologetically back out of it.
This is why people hate me. This tendency of mine drives everyone crazy, even other NPs. The extroverted people are usually too good at worming commitments out of me and then get pissed when I don't follow through.

Is this a normal INFP thing?

And what is one quality/mannerism for which people dislike you? I think we should be able to learn from this thread, not wallow in self pity. Or at least gather strategies about dealing with more strong and insistent personalities.