Luck is a significant part of fantasy football.
One topic I haven't seen mentioned is to know your league(s). This matters in several ways:
1. Scoring system -- know every aspect of your league scoring system
2. Roster size/lineup configuration -- the size of your bench and lineup options (if any) can and should cause you to alter your draft and waiver strategy
3. Learn each league's tendencies, both individually and collectively. If you compete in the same league for several seasons, tracking other owners typical draft preferences can help you attain more value in your picks. In addition, knowing the collective personality of a league enables you to know when to be aggressive vs. patient in drafting specific positions, sleepers, etc.
4. In-season player movement also can vary highly league to league. Some leagues have near-constant trading, others average one trade per year or outright outlaw it. Many leagues have that one owner who grabs every waiver wire wonder, so you must outbid (if a waiver bid league) or take a chance on an emerging player a week or two early if you strongly believe in a given player.
It's important to enjoy the process, win or lose, to the extent you can. If you aren't enjoying FF, it's not worth your time, but it also becomes difficult to do the little things mentioned throughout this thread that often prove to be the difference between a mediocre, good, or even great season.