Ann Logan

Tension in your stitching is by far the easiest thing to correct, especially if you’re using a hoop – pull tight but not so tight that you stretch the hole at all. If you stitch in hand you have to be more careful.

I find that pulling the thread mostly through and then using my little finger in the hand holding the needle to “flick” the tail the final bit gives perfect tension and is reproducible for each stitch. Pay attention to the tension you’re applying as, if you stitch in different directions or do “patches” of stitching over the piece, you’ll pull it in weird directions.

Remember, cross-stitch is considered counted embroidery.
So count count count count again and double check your counting. It really helps minimize mistakes.
Gridding save you a lot of time (and your sanity too). Cross stitch is meant to be relaxing. Make your hobby hugely beneficial for your mental and physical health.