You're not alone, trust me, it kind of scares me how many people I've encountered who have no control over their emotions. One thing you have to accept is that the feelings you experience when you lose/get rolled/play poorly aren't going to go away and, short of death or various drugs(not recommended), nothing is going to change that. However, there are many things you can do to make it manageable and even in some cases less potent of a feeling.
For me personally, I think what helped was repetition. I played the shit out of comp tf2 for several years, getting rolled and eventually seeing progress in my performance and my peers. Nowadays it's pretty easy to control myself as far as getting angry or sad goes because I have a lot of experience with it and I've learned to develop my own coping mechanisms/solutions.