Unlearning Passive Agression

Ok, so now for something a bit more heavy than recipies for soup.

I've got issues. Of course, we all have issues, but after being beaten over the head for several months by someone who cares, I've started examining one particularly large issue I have:
Passive Agression.

This is particularly difficult for me to approach, because I hate passive agression in other people. I suppose that's how it typically goes; what we dispise in others is typically our own faults in one shade or another. Still, admitting you have faults is particularly hard for we passive-agressive types. ;)

I came to the conclusion that something has to be done. I need to find a way to identify these things I do before they happen and derail them before then end up hurting my relationships.
Specifically, my relationship with my boyfriend is suffering greatly due in part to this problem.

So far, I've determined that I have a serious habit of deciding to forgo expressing when I dislike something he is doing because I have a real fear of saying no to him. This is a pretty general statement, but it covers a TON of different events over the last year...hell several years. He goes along thinking I'm cool with something and I end up screeching over something far less important and pissing him off. This happens to be THE number one pet peeve for Ryan, the thing he absolutely will not tolerate, so changing it is important to me.

The question is: How? How do you do that?