Yes, some point. I've had problems winning won positions, but not recently in serious games (blitz isn't serioius chess). I just grow bored winning my games in blitz because I ...f I know why =(
Blitz sucks

Read reassess your chess by Silman...trust me, I used to have a problem when I would get up say an exchange with clear advantage. I would no longer look for the strong moves and I would kind of wait for my opponent to resign...the they got counter-play and came back and won:/...Then I went throught that book and no longer have that problem. I dont think your problem is with blitz, its with winning won games...but if it is the blitz, dont worry...blitz blows anyway
You recommend that book to everyone.
And I can sort of understand saying bullet sucks, but blitz is by far the most common form of online chess games. It is also highly instructive.
How can I make is suck less?
A lot of my games go (when I'm somewhat concentrated) like this:
* Get to play an variation I want. Eventually I gain the advantage, win a pawn or two or even a piece. Lose interest, opponent doesn't resign despite being down gazillions in position. I lose even more interest, get in time trouble and either lose on time or blunder something in the end - or both.
Which eventually leads to me not renewing the effing ICC account because blitz suck =) I got around 2000 Elo but in blitz and especially online it's horrible. How can I make blitz not suck so badly? Or even find it fun winning my winning games.