To max out your stats, during the week of a game when you are on a game day, 
select the game. You will get the option to play or sim the game. Go back, then 
go to the Performance Institute. Go to whatever drill you can. Keep repeating 
this process until you have the desired attributes. Note: This will decrease 
your stamina. The best option is to turn game fatigue off. Note: Stats do not 
completely carry over to the next week, and if you simulate your games your 
performance will be affected by the weakened stamina. Turning off game fatigue 
only works if you actually play the games.

You can increase your Overall, Awareness, and Stamina in Practice mode by having 
your superstar get practice points by getting a big gain on offense or creating 
a big loss on defense. You also can get your stats up by getting an agent that 
has access to the Performance Institute and get a medal on it:

Bronze: 3 points 
Silver: 4 points 
Gold: 5 points 

Note: Your stats are not permanent. They will be reset after each game. You must 
do the practices and Performance Institute again to get them back up.