"Das Glück ist keine leichte Sache: es ist sehr schwer, es in uns selbst, und unmöglich es anders wo zu finden."

(My) translation:

"Luck is a difficult concept, it is very hard to find in yourself, but impossible to find elsewhere."

(Source: Arthur Schopenhauer, Aphorismen zur Lebensweisheit)

An interpretation:

Be your own best friend. Try giving yourself and yourself alone some enjoyment every day, even if it seems small such as going for a sunny walk or drinking a good coffee or whatever it is, that heightens your senses and brings joy to your soul. Just make sure, you do it only for yourself and that it does not depend on other people. The search for external validation will lead to nothing but vanity and bitterness, regardless of what media and popular culture try to inject into your brain.