New Challenge is a challenge

It seems like if I win at Full Tilt, I lose at PokerStars and vice-versa. Overall, I am slowly moving my bankroll in a positive direction but I won't be moving up to $15 and $20 dollar challenges anytime soon. I will need at least a week of good solid play to finish off the $10 dollar challenge.
I tend to win more than just $10 when I win and have been losing a little more than a buy in ($25) when I lose. This is because I am multitabling and I may have wins on several tables and then make a nice pot to clear the challenge for the day and that puts me over the $10. Most of the time I am at $20 in wins when I quit. The opposite is true when I lose a buy in. I may be down a few dollars at a couple of tables then drop a big pot and that makes me lose more than just one buy in.
My discipline has come into question, too, as I oftentimes will win a buy in after only about 15 - 30 minutes of play and I am hesitant to quit as I feel I can win even more money. One night that bit me in the butt as I continued to play and lost a buy in with one of the aforementioned Set over Set hands.