Brett Steenbarger has some excellent suggesions.
"Never lose so much on a single trade that you can't come back and be green for the morning or afternoon;
Psychologically, it's healthy to experience defeat and then overcome it. It strengthens you to battle back and win. If you lose the wrong way--by taking so much risk that you can't come back for the day, week, month, or year--you rob yourself of the victory that could be yours by going from red to green."
What happens after strong upside Momentum Days?
Larry Connors in his book "How markets Really Work" has done a lot of study on market behavior after big up moves. His conclusion is that the market takes rest for the the next week or so. New gains come after at least a week.
This tells us:
After a big up move, buying on further breakouts may not be profitable since such breakouts could be quickly followed by declines.
Selling short in NOT profitable since the markets will resume their advance, most of the time, after a pause.
Buying on dips seems to be a safer method of trading the market after a big up move.