Iakobos
Orthodox
This is one of those platitudes that everyone loves repeating, and it seems really meaningful until you actually think about it. What does it actually mean in terms of a concrete course of action to "find happiness within yourself"? Get money and muscles? Get a hobby or a passion project? Sure, those things are all great, but I have not found that they can fill the wife-and-kids-shaped hole in my heart.
My hobbies don't fill it. Computers are my craft, and I find meaning and money in it, but it doesn't fill it. Money and the gym definitely don't fill it. Faith fills an entirely different hole. I am still a very lacking neophyte, so maybe if I just practice the faith harder and for a long enough period of time. I don't know.
Men and women mystically complete each other, creating a family is co-participation in the act of creation of life with God, nothing else is supposed to fulfill this hole other than a specially granted vocation from God of either celibacy or childlessness from infertility. Which the vast majority of men are not cut out for. So it's natural for you not to feel that your work or hobbies fill that hole, they shouldn't.
I would maybe revise the phrasing from finding 'happiness' to 'outcome independence.' Being willing to accept whatever happens, which as Christians we know is God's will. We will all bear a cross that doubles as a gift from God, we just don't know what form it will come in. In the meantime do the best you can in terms of finding a woman while maintaining your professional objectives, but despondency is from the demons. You're early-20s, you have easily 10+ years to find a good woman, take heart.