Subscribe to the sunken cost fallacy. What round you draft someone in becomes meaningless the second your draft is over. Do not be afraid to cut bait/trade someone because, "Well they were my 4th round pick". Well, sucks for you, but that 4th round pick is currently returning 13th round value...NEXT.
One caveat to this rule:
For the first few weeks, never bet on lotto tickets on the wire unless time opens up due to injury. It's early, it will usually regress (either way) to the mean in a few weeks. Just because CJ Miles starts off hot, doesn't mean you should drop a valuable piece that you just drafted to chase the lightning.
I usually won't make my first roster move (barring injury) for at least two to three weeks. Its too small a sample size to know what you need to be focusing on (in Cat leagues, I don't play roto) before then. Until you get to around Thanksgiving, there's no hole too deep to dig out of in the standings. Keep patient, analyze your team so you know which is the best path forward. Once you start managing from your heels, it's almost impossible to tighten the reigns again.