Regularly yank, stretch, pull, pump, squeeeze, whatever, sooner or later you will cause nerve damage to your penis. And because nerves have memory, you might not suffer the consequences immediately but weeks or months later.
Moreover, if you view overall well being as an interconnection of all our parts (body, mind, spirit), as I do, then don't be surprised if excessive crank yanking results in emotional/psychological problems including depression and anxiety.
A few millimeters either way just ain't worth it, in my opinion.
Accept and love yourself, especially your sensitive bits.
Peace, baby.