I learned to sew first on my great-grandmother's treadle Singer (WISH I had that machine). Gram was all about perfect tension, so from the beginning, say age 4-5, I've been adjusting the tension without being told it was "bad". The secret is "go slow with tension changes". The other secret is to run a practice stitch, something you'll be using in your project, and carefully examine both the top and bottom threads for precision tension. Only adjust one tension at a time (upper or lower) or you'll never learn how each individually alters the tension. Never move the screw in the bottom tension more than 1/4 at a time. Always use the same type/thickness of fabric/quilt sandwich that you'll be sewing on. Once it's perfect on your experimental fabric/sandwich, you can just start sewing.
DO write down the original position/tension number at the beginning so you know where you started. DON'T be intimidated by your tension! You really can't mess it up so much that you can't fix it. If you could, surely I'd have done it at some point over the last 50 years! LOL!