What kind of mental attitude must a poker player strive to have at all times?

A poker player must be cool and calculating. He/she must not be results oriented but rather, make positive expected value decisions which are sure to be profitable over large sample spaces. A poker player must focus on always making the right decision even if doing so requires great courage. He/she must show courage and composure when a hand doesn't go as desired or when in a down streak. And a poker player must never lose the desire to win. Sometimes the only thing that separates two poker players is that one wants it more than the other and that one will be the bigger winner. All of this is not easy to sustain for a long time but it is the attitude of a winning poker player.

A poker player must strive to be focused at all times, above all else. Focused on the cards, focused on the other players, and focused on your surroundings. Lose focus for an instant and you may miss an important signal that could make or break you. Or you may make a bad decision because you lost focus for a second, and suddenly you've got middle pair with a medium kicker and the guy across from you is putting you to some serious decisions. Listen to the pros, they will say that the toughest part of playing in tournaments is the ability to stay focused for long periods of time. Poker is a mental game, and you can't win if you're daydreaming about the cocktail waitress.

You must maintain a positive attitude.

This positive attitude is developed by being focused on the game, knowing the proper odds and hands to play, reading your opponents and being confident in your skills and ability.

Good luck!

Staying cool.

all the mental attitude wont change a two into an ace

Well, when i play i try to seem uninterested, and bored, as if i know im not gonna win

Be optimistic!