One thing I can speak to is this: you say you don't play SNGs often because you don't always have an hour to spare.

If you can't sit for a couple of hours, it may tend to get frustrating when you don't have a winning session -- since a session for you may tend to be shorter than it ought. As a result, you may feel the need to take unnecessary risks in order to make THIS session a winner.

Seems that you ought not to sit down to play until you have a few hours you can devote to it, IMHO.