How can testosterone possibly increase both aggression, and well-being at the same time?

I can answer that!: If i were suddenly converted in a raging bull and everyone were so afraid of me that they would do anything to keep me happy....Heck, i'd feel pretty good too! haha! seriously, though...Testosterone (as all hormones) don't just affect one single organ or part of an organ. When in normal amounts the whole brain is appropriately stimulated to interpret its full spectrum of emotions.