How not to tilt at the beginning of the tournament?

If you are on tilt right from the start, you need to exit quickly.
You need a lot more patience in the later stages, so if you are on tilt right at the beginning, it's not a good sign for the later ones.

As Royal Road says, AA and KK are good starting hands, but can always lose. However, whenever you play them - early or late in a tournament - you should still take position and your opponents' way of playing into account. Don't let KK under the gun fool you into going all-in at the start of a tourney - always better early on to be cautious (unless you are desperate).

It's simple, just don't make risky moves, or huge bets, without strong cards, at the beginning of the tournament!