Awareness ties in with all other mental toughness areas. Take concentration. Lets say a person is 4-0 up first set, and they relax as they are way up, and a person does not realize – “well that shot was careless” after maybe trying an extravagent dropshot, that person may make a few more careless errors. In actual fact, a mentally tough player would be AWARE that the set is by no means over and that they have to stay focused and intense.
Many negative thoughts do appear during a match and if a player does not become aware and know to ignore the thought, it could really be a problem. So are so many difficult obstacles that face a player. You have to play automatically during a point. No conscious thinking during play! A huge thing as well is to always play positively and agressively. In the Mental Manual For Tennis Winners , Tomaz Mencinger states the following:

“Nothing positive can come from being negative”. That is very true. You will often see a player get up by playing good attacking tennis and then the player serves for the set and suddenly stops hitting the ball. The player got ahead by playing agressive. Why stop? Many players are scared of losing. They play not to lose instead of playing to win. If you play agressively and do not win, thats OK! You have given yourself the best chance of winning. Always play to win, thats the only way to go! The way to see this is – it MATTERS but it doesnt MATTER.You want to win but if you dont its fine. You accept it.
Paul Henri Mathieu is someone who plays great agressive tennis, and is mentally aware. No matter what the score, he will just play! No thinking, just automatic, as many pros.