You don't need to impress people by saying yes all the time. Saying NO is your ticket to sanity and peace of mind. That's is self-care.
Knowing when to say NO prevents you from feeling resentment, overwhelmed or stressed.
Of course, saying NO when you needed to say YES is not adviced.
Say yes to opportunity.
Say yes to experiences
Say yes to happiness
No means no. Respect your feelings. No need to justify or make excuses about your reasons to yourself and others.