FtM? I would imagine you meant MtF, right? Mostly because I don't know many FtM that consider testosterone blockers.
Transition is about changing yourself. This is not merely a bodily change for everyone... I changed my personality as well. I went from being quiet, angry, and passive-aggressive, to more expressive, sassy, and outgoing (and still a little passive-aggressive, as people enjoy pointing out). Going on testosterone blockers and estrogen often makes one more vibrant, and to be honest... I don't feel one bit more passive. If anything, I put up with less than I used to - and I'm still just as competitive, in attitude.
Of course, I can only speak for myself. However, if hormones are right for you, then they tend to make you more confident. Confidence tends to counter passiveness and weakness.