I added a lifeline (a bit of thread) before I started the heel on a new short shortie sock. The last pair I tried to knit was fraught with errors to the point I gave up and reached for a new ball of yarn. With a lifeline in place I can unravel and rip back if I need to. Safely.
So far so good, the heel has been turned and it's just knitting round and round, mistake-free.
