Tucking chin in when punching - Muai Thai / Boxing

Greetings;

I recently took up a Muai Thai class (after kickboxing) and am trying to adjust 'bad habits' that have been engraved in my psyche over the past years of self training followed by a lax kickboxing training.

I'm having a lot of problems keeping the chin 'tucked in' while punching. I understand the concept of protecting the chin from incoming punches while throwing a punch (makes sense; I got a ringer once from an uppercut and protecting the jaw has been priority since)

The problem I have is I find myself constantly falling back into old habits and having to concentrate to alter the technique (tuck in damn it). It also doesn't feel 'right'. Between that and keeping eyes on the opponent I find it uncomfortable and I feel like a hobbit. Does anyone have any advice that might help with where the head should be (other than just tuck it in) or making it habitual other than 'keep doing it over and over'. The latter being my current 'go to' option.

The only other thread that came up on a search was mostly questioning the validity of tucking in rather than assisting in making it habitual.