My wife is MTF and keeps telling me that I will have a fair amount of aggression to deal with when I start T and that instead of getting upset and crying I will get upset and be angry.  Is this what I have to look forward to or is there more involved? Will the disciplines I have in place to handle my anger/temper still going to be in place, or will I have to work on new ones and hope I don't loose it before I have disciplines in place? This has been majorly on my mind and am afraid of how much of a problem it will be.

teenage boys seldom cry but they do get angry so you can look forward to it...and spotty oily skin
the T will give you a second puberty or actually a proper first puberty to make up for the messed up one all genuine TS have.

I always felt that hormones, both T and E, can give a boost to feelings which you have but they do not control you. Like with aggressiveness I think T can enforce that if you let it. And being horny with T... personally I´m happy to be free from that now but it is controllable. 
E can be more emotional. Emphasizing the CAN part of these things.
These things are highly personal (like everything) even if there is some common and more usual characteristics. I believe that the idea of us being slaves to our hormone is false and even a terrible thought.

I agree with julo.  I know a couple of FTM's who never got agressive after their T because it is not in their nature.

is upset and being angry the same as aggression?   I don't think they are the same thing at all.

I really think you should ask the guys this question. The effects of testosterone on a girl-brain and the effects of testosterone on a guy-brain are just not the same at all. T made me kind of psychotic, but most of the guys tend to say it makes them feel more stable and in control. Girls who've suffered through testosterone poisoning are kind of the worst people to ask.

Well, when I had more T in my body, I rarely rarely got angry (or if I did, it was easy to control). Though, when I was in my young teens my anger was more of an issue.

So, you might have a period where your new emotions run away with you (kind of like MTF's emotions do). But eventually you will get over it and it won't be so bad (and you will have new tricks to deal with yourself).