Big leak. Playing less when ahead, more when behind, need help

[1C5]

This is probably my biggest leak. I am a 99% SnG player and here is what happens:

If I do well my first couple of sets and am up $150 or $200, I start thinking that one bad set (I 8 table) will bring me right back to even so I am "scared" to play more.

And if I start my first couple of sets badly, then I will play more as I don't like losing obviously.

Now to fix this would the best thing to do is set a time (either hours or number or tournaments) that I will play or can you suggest something else?

[gildwulf]

Play X number of sets, take a 10-minute break and walk around the block or something, call a friend, or something that has nothing to do with poker. Rinse, wash repeat.

So say play 2 sets, take a break, 2 sets, take a break, 2 sets stop. After you become used to this schedule bump it up to 3 sets, then break, etc. Then more and more and you hopefully will get psychologically used to playing a large number of sets at once without going on tilt...

[SheetWise]

Is this possibly just a bad analysis of a player who loses more often than he wins?

[1C5]

Well I just started playing in January and am up 13K since then, so I am confident I am a winning player. Still haven't had a down month and rarely a down week.