Catch some trains, get knocked off of some, ride some. If you get a decent ride then it was one of the right ones. If not, hang out for a bit, another will come along. Easy enough to see at the end of the day which ones did best. One thing for sure though. If I wasn't on it, I didn't get to ride.
One other thing. If I have been waiting for this train(setup) and I don't jump on, then to me it is surely a psychology issue. For one reason or another I haven't accepted the risk of the trade and plain old fear of losing my money has caused me to hesitate, then I watch it run a bit and tell myself something like, "I'm not going to pay five points higher( futures) than my entry target, what if it pulls back" so I wait for a pullback or a deadcat bounce(depending on direction) Then either it doesn't pullback/ or not quite enough, takes off again.....lol.....now ten point move.....and I say to myself - sure better not chase it now...... I suppose this happens to almost all traders at some point in time. It happens to me more often than I care to admit. I am working harder to catch more trains when my simple little method says so. But I by no means catch them all.