The most consistently miserable people are those who can't be happy unless everything always goes their way.
The most consistently happy and fulfilled people are those who decide to enjoy and make the best of whatever comes their way.
It's great to expect the best for yourself, because your expectations drive your reality. Yet life will deliver many unexpected twists, turns and disappointments on the way to fulfilling those expectations.
Making yourself miserable about those disappointments and misfortunes won't achieve anything positive. Stop and think how much more effective you would be if you could simply accept those disappointments and then move on past them.
Expect the best, and make the most of the rest. That's the quickest way to get where you're going while finding plenty of joy in the precious moments along the way.