"Sure other people have had problems with drugs, but I'm stronger than them. I'm sure I can take this for fun and be just fine afterwards."
"It's not necessary for me to put too much effort into my studies. I'm already a special and brilliant person, so it's a waste of time to work too hard."
"There's no problem with me putting this holiday on my credit card. I'll just work harder and save harder next month to pay it off."
"The road rules don't apply to me like they do other drivers. I'm an excellent driver, so nothing could possibly go wrong."
It's what you do that defines you and creates success. How optimistic you are is virtually irrelevant.