I've see pussies in MMA all the time whatchu talkin bout willis? A lot of people give up in fights, they may not throw in the towel but they stop trying. It happens at least once every PPV. You don't have to actually leave the ring or octagon in order to give up. And a lot of people use the terminator method to cope with their pain and such. When you see a fighter come right back at you after getting rocked it doesn't usually mean they want more, it's just instinct really. Also another example of a professional MMA fighter giving up during a fight is Jeremy Horn when he faught Chuck the second time. He straight up said "I'm done". I don't think every instance of coming back after getting rocked is a show of heart. I think you can tell while you watch it whether it's heart and determination or just their own way of coping with the pain of getting rocked and trying to get an audience reaction to boost their confidence AND to freak his opponent out a little.