so what should I do if I'm feeling p****d off?

the answer is probably do something you like doing until the feeling wears off.

But the problem is, when I'm feeling this way I think I have to change something.
And then I want to change something big, something worthwhile.

And then I'm either stuck because I'm daunted by something big and don't think I can manage the challenge or I make a start and after a while (my usual time is about 4 days) I can't sustain the new direction.

I probably can't sustain the new direction because it's not giving me any more satisfaction than the old one. Which means I'm changing the wrong thing. And this is a big worry to me because why change from a OK me into a new thing that doesn't work if it's forever. Better the devil I know type of thing. Which leads me back to the worthwhile thing.

New idea - if I have to make a change....then I'm going make a change about something small. something that will change the quality of my life. I'm going to change something small that is annoying me, something that's just niggling at me. In this way the change is done, doesn't have to be sustained unless it seems to give something back.

All that said - it is worth putting a time boundary on even the small changes. Do this in 5 minutes. Do this for 3 days this week. Do this for a month. If I don't do this then I don't do things because I have all the time in the world. And I'm not committing to forever if things aren't working. If things do work and become part of life all for the better.

Adios self development stress.