The best way is always to stop when you are going good and when you know what will happen next. If you do that every day … you will never be stuck. Always stop while you are going good and don’t think about it or worry about it until you start to write the next day. That way your subconscious will work on it all the time. But if you think about it consciously or worry about it you will kill it and your brain will be tired before you start.

(more detail: http://www.secondactive.com/2009/08/boost-your-productivity-...)

I would also add 9a. Understand what was causing the bug once it's fixed. I'd say a key hallmark of a bad engineer is if they are happy with a fix even though they don't understand what the underlying problem was.