You ask how I manage to stay involved and remain seemingly happy and adjusted to this awful world where the efforts of caring people pale in comparison to those who have power?
It's easy. First, don't let "those who have power" intimidate you. No matter how much power they have they cannot prevent you from living your life, speaking your mind, thinking independently, having relationships with people as you like. Read Emma Goldman's autobiography LIVING MY LIFE. Harassed, even imprisoned by authority, she insisted on living her life, speaking out, however she felt like.
Second, find people to be with who have your values, your commitments, but who also have a sense of humor. That combination is a necessity!
Third (notice how precise is my advice that I can confidently number it, the way scientists number things), understand that the major media will not tell you of all the acts of resistance taking place every day in the society, the strikes, the protests, the individual acts of courage in the face of authority. Look around (and you will certainly find it) for the evidence of these unreported acts. And for the little you find, extrapolate from that and assume there must be a thousand times as much as what you've found.
Fourth. Note that throughout history people have felt powerless before authority, but that at certain times these powerless people, by organizing, acting, risking, persisting, have created enough power to change the world around them, even if a little. That is the history of the labor movement, of the women's movement, of the anti-Vietnam war movement, the disabled persons movement, the gay and lesbian movement, the movement of black people in the South.
Fifth: Remember, that those who have power, and who seem invulnerable are in fact quite vulnerable, that their power depends on the obedience of others, and when those others begin withholding that obedience, begin defying authority, that power at the top turns out to be very fragile. Generals become powerless when their soldiers refuse to fight, industrialists become powerless when their workers leave the jobs or occupy the factories.
Sixth: When we forget the fragility of that power in top we become astounded when it crumbles in the face of rebellion. We have had many such surprises in our time, both in the United States and in other countries.
Seventh: Don't look for a moment of total triumph. See it as an ongoing struggle, with victories and defeats, but in the long run the consciousness of people growing. So you need patience, persistence, and need to understand that even when you don't "win," there is fun and fulfillment in the fact that you have been involved, with other good people, in something worthwhile.
Okay, seven pieces of profound advice should be enough.