Optimism means expecting the best, but confidence means knowing how you will handle the worst. Never make a move if you are merely optimistic.

Optimism can be a speculator’s enemy. It feels good and is dangerous for that reason. It produces a clouding of judgment. It can lead you into a venture with no exits. Even when there is an exit, optimism can persuade you not to use it.
You should never make a move if you are merely optimistic. Before committing your money to a venture, ask how you will save yourself if things go wrong. Once you have that worked out, you’ve got something better than optimism. You’ve got confidence.