I know I've written about this before but reminders are always good!
When you practice a difficult passage, you don't always need to change something to make it work. In fact most of the time, it'll correct itself without you doing anything about it after a while. Your body just need some time to develop the right reflexes. Just because something doesn't work doesn't mean that you're doing something wrong. If you try forcing things, you might get some short term results but you can also develop bad habits.
By playing a passage without trying to correct it, you let go and trust your body to make the adjustments. You stop acting physically about it and let your reflexes take over. This will work once you're beyond the stage of learning the piece and are working on polishing it. It will make your playing more fluid and relaxed.
It's a bit like when you play video games. At first you're not good at it and get defeated by the small monsters in the beginning but after a while, your reflexes adjust and you start fighting the bigger ones and beat them without having done anything special. You're just playing and having fun. You very rarely have to "change" anything to become better at a particular game. It just happens over time as long as you keep playing.
If something really won't work and you keep missing the same notes all the time, you might want to take a few steps back and practice the passage slower. If it's something high, maybe your chops aren't ready for this piece and need more time to develop some strength. Or it could be that your air, chops and fingers aren't well coordinated. In this case, letting go and playing without trying to correct the mistakes can help you as this is often the result of tensions in your body.
In any case, remember that learning a music instrument takes time and patience. There is no magic wand that will solve all problems right away! Just keep doing what you need to do day after day and you'll improve over time. The good news is that you can still have a lot of fun even if you're not the worlds greatest player!
I am associate principal horn of the Singapore Symphony Orchestra and the author of the progressive methods. I'm happy to share my experience as a horn player and teacher with you.