Plus the actual physical release of it.
I never really fought (the qualifier because I came close several times and I was ready) so I don't miss it. But I do enjoy opportunities to be confrontational if the cause is right. As in, I only like it if it's justified. But if it's justified, it's fun.
For example, I just joined a new gym. They have personal trainers who hardsell the heck out of you. I pity the fool who targeted me. He was relentless, and I really let him have it. (I was polite and controlled the whole time mind you, but I stood up to him in a way that clearly surprised him, and figuratively ground him under my heel.) That was awesome.