1. Focus on your own game
2. Try to track the weak players on your table and wait your chance to hit them
3. Don't get distracted with other things like kids, wife, sport event etc. Better play 2-3 tables, than to split the focus.
1. Make mathematically profitable decisions and act according to your tournament situation.
2. Don't let your emotions affect your game. Try not to open poker clients when you're upset, obsessed with some problems or drunk. Leave the game when you tilt. Composure is of paramount importance!
I just imagine every hand l as ordinary Math task. It's really very helpful to block emotions and make more profitable choices but took a lot of energy.
Making a nice decission , and try to play relaxed to control your emotions as someone already told you here. Patience also is a important thing in poker.
To stay calm , cool , not to get angry on bad hands/bad luck , no tilt not think mistakes while you play , a lot of patience as many said , play right hands at right positions and with the right bet size , so be alarmed/awaken as much as you can .