It happens to everyone. And some things may work well for one person while other things may work for someone else but here are some ideas. Some coaches push, this isn't common anymore and is highly debated but it was how I was coached and the only thing that worked for me. My coach didn't let me chicken out, if I did I got some form of punishment, laps, pushup's etc. after doing so many of those you get tired of it and get on with the skill. That approach doesn't work for most people though. Another thing is completly oppsite, go back to basics, do a roundoff rebound like 6 billion times, do standing back hand springs a bizillion times, do round off pause back hand spring over and over, do round off back hand spring with a spot, then a very light spot then no spot then add a rebound, after that works do round off back hand spring tuck jump, then add some mats for height and do the tuck jump up onto them. If you know how do some standing back tucks. Envision yourself doing the entire skill perfectly take a deep breath and have the coach spot the first few, then spot more lightly, then maybe try it with a sting mat, finally envision yourself doing it perfectly take a deep breath and do it. Lastly since it is a series of skills not just one when you go to do it think run, roundoff, tight, back hand spring, eyes up, spot, set pull, tuck. Break it down don't think omg I have to do a backtuck. Keep in mind this won't work over night it might take weeks or months depending on you. Good luck, and no worries you will get it back!