[This is a very personal decision and there are no wrong choices and your gender is real no matter what you do or don't do, and if you change your mind that's real too; all things are possible when you understand you never deserve adverse consequences, internal or external, for Doing Gender Wrong.]
DO IT.
This was exactly my experience too, spending years umm:ing and aah:ing about whether I wanted to transition. Around this time two things happened that swayed me: a friend gave me pretty much the exact advice as in the original post - and I read Julia Serano's Whipping Girl. I decided to give it 3 months and see how I felt then.
I felt amazing, I loved it, I never ever want to stop.
Also, "I simply do not think that way about things I actually don't want to do." is such a perfect encapsulation to help clarify that state of mind.

