He said: "I will not say that I'm a kind person or a good person. I can only say I'm a really calm person in life.
"I actually have no idea why the demons go out when I play tennis.
"Especially when I was a junior, I had a lot of problems with my attitude. I was not getting defaulted, but I was getting - to have a game penalty was easy.
"I was working hard because every time I do something wrong on the court, I'm sitting with myself, I'm not like this in normal life."
The 23-year-old says he is continually working on his temperament and wants to take time to process a remarkable summer which closes with his first grand slam final.
"Why does it happen? I don't want it to happen like this. So I have been working a lot on it, and I have improved a lot.
"Sometimes it still happens. But again, talking about normal life, to make me angry, you need to do something crazy for one week in a row.
You need to, I don't know, come to my hotel, knock on my door at 6:00 in the morning for seven days in a row. Then I'm going to be maybe mad a little bit. If not, I'm really calm.
Medvedev added: "This summer's been, I should say, so fast and long at the same time.
"Long because I've played so many matches. At the same time so fast because, as you say, I didn't have any moment to just sit down and look back and say, Okay, I've done amazing things. Hopefully, I will have some time after Sunday."