I’ve done this before trying to brainwash myself while I sleep with sanskrit mantras and prayers. These youtube affirmations work even better for me.
I believe that in a healthy attachment process the child would subconsciously absorb positive self-beliefs (these affirmations) from the parent through their body language, energy field, and behaviour. Lacking the vibrational template of a parent, you can simply reprogram your subconscious while you sleep with these videos. It could also be setting an intention that makes it work. Pick one and stick with it for a few days.