Remember that sometimes, the game just fucks you. The best magic players in the world have a win ratio of about 75%, sometimes your opponent just Godhands while you're stuck on a onelander. Generally speaking, you never mull below 5 on the play or 4 on the draw
Except against Legacy/Vintage dredge where you mull to 1 trying to get your Leyline of the Void or they just end you.