I think ones mental apporach to sundays plays a huge part in success or fail.  I personally like to relax Saturday nights and get a good nights sleep. In the morning I try to get a good healthy meal and a coffee in me before I play. If you can get to the gym or do some kind of physical activity I think it will get you a clearer mind before you play too. You really have to go into Sundays wanting it bad and plan on winning. Try to block out past Sunday failure and really focus on positivity no matter how bad your first few tourneys may go in the day, there are lots more to be won.

Poker wise, the only real adjustment I make is trying to keep tables down. 8-10 and no more on Sundays is what I prefer all day. The higher the buyins the less tables you should be playing imo. I grind all stakes and mass table all week for a reason, to build a roll and confidence for Sundays to focus on making real money and hitting that big score that matters.