That is funny. As a child my mother would also say don't touch the tension. I'd like to dispel the fear out there for
those who don't know about tension.
My husband and I restored and collected many machines and sold most of them. I have old machines and newer computerized machines. Tension does not change because a machine has a computer in it. It is a nice feature that with most new computerized machines, the tension if changed reverts back to factory default.
Due to fabrics differing in texture and needle size usage, you really should be comfortable with changing tension.
The ideal tension on your machine stitch should have the knot sandwhiched between the top and bottomfabrics. If the knot is on the top fabric, the tension is too tight. Thus, lessen the tension. If the knot is on the bottom fabric, then the lower tension is too tight and you need to increase upper tension. It's kind of like a tug and war. If you cannot adjust the tension to suit you, then you may need to turn the bobbin screw that adjusts tension, this should only be a slight and minimal turn. Tightening that screw to the right, makes the bobbin thread tension tighter, left turn makes it looser.
Sometimes tension problems are also caused by needing to change a needle, clean lint out of the feed dogs and remove the cover plate to remove any lost small pieces of thread and lint. You may need to look closely, as very often there is a wedged in piece of lint in the feed dogs at the farther end of the feed dog.
Most of the machines I've cleaned and readjusted tension too had problems simply because of threads, lint, dust and dirt. Patience is the key to keeping a machine running perfectly. (There was a time I was afraid to do anything to a machine, and if I can do it, anyone can.)