Be optimistic about your end game but be realistic about your life.
Optimism will drive you to achieve great things and take giant risks. Optimism will take you on great adventures and you will do things you have always wanted to do. Optimism gives you permission to have enormous goals and vision for your life. Optimism lets us see the good and the potential in people. The world would be a depressing pessimistic place without optimism.
The downside of optimism is that it will blind you to the risks. It will cause you to take giant chances that you shouldn’t be taking. Optimism will make you take enormous loses that are hard to recover from. You have to use realism and pessimism to mitigate your risk. How likely are you to succeed? How likely are you to lose? You must be completely comfortable if either one of these situations happen. Don’t be naive to the negative.
Knowing you are protecting your downside allows you take bigger risks. It is a fine balance you must walk because if you are always preparing for your downside then you will not take massive action for a huge upside.