A jab with a quick RETURN

Practice. Sparring in particular. If you have a lazy jab a good sparring partner will punish you for it. You'll learn not to be lazy with it, because taking punches is unpleasant. You could also simply practice on pads, during drills or on the bag, but if that doesn't work learn the hard way.

Just keep doing "skills" related work and focus on bringing it back quickly. If you pay for your mistakes the brain tends to remember it, so pain can be avoided in the future.