Well being a quitter will not put you in good standards with other people. Just set yourself up to compete in games/matches that are good for you with respect for the amount of time you take. If you think that you need more than 5 minutes then settle for a 10 or 15 min game. You dont need to worry about the clock and your enemy. The clock can be an enemy too if you play matches with not much remaining.
Still play the game to the end no matter what. Accept the loss but fight for every piece if you know you are in a losing fight. Who knows, your opponent may just slip and give a vital piece or two away and throw away his initiative.
Experience is the best teacher, so play, play and play. Just dont forget on what you did to get you there.
My friend had his account banned for abandoning games when he abandoned games where the person was taking excessive amounts of time to move. Do I have anything to worry about?