It's not nagging if you only do it once and do it assertively. If he doesn't do it after you remind him nicely once then fine, back off. But I don't think it's nagging to pull him up on it if it's important to you. He seems like he does want to change, give him the benefit of the doubt. You could even frame it slightly differently 'I noticed you haven't been sending goodnight texts as you agreed to. It would mean a lot to me if you kept doing this *insert reason here*, but if you're tired last thing at night then maybe we could change the timing of the texts. I'll leave it up to you to think up a solution'
Would that work? How important are the texts? Or are they a test of his commitment and ability to change something small? Could you ask for something else important instead?
