I completely understand your fear. If you are concerned about ruining your quilts... start with a small simple project that you have not invested a lot of time making. Table runners, placemats, lap quilts or baby quilts are a good place to begin. Confidence comes with practice. Google "free motion quilt tutorials" or check out youtube for inspiration. Don't expect perfection, just do the best that you can. Everyone has to start somewhere. Just relax and enjoy it.