I don't know of a specific technique or anything simple to recommend, but I think I can say something useful nonetheless.
I think there's a way schedules can loom large in human minds, shaping our experience of reality where we feel ourselves to be within the schedule, routine, or whatever you want to call it. It comes to feel familiar and we have expectations around what will happen now and next and that shapes our perception of each moment when we believe ourselves to be held by the schedule.
Of course, the schedule doesn't really exist; it's a construct that exists only to the extent we believe in it, and therein lies the trick. Whether or not you feel flexible or if you feel like you've given up depends on your relationship to your expectations for what is going to happen. You can pay attention to the way this relationship forms in your mind, changes under different circumstances, and use that as a jumping off point for freeing yourself from feeling one way or another because you slept in or are keeping your routine.
I wouldn't recommend trying to avoid giving up or anything like that, though. Rather, I'd suggest just noticing what happens when you keep or don't keep the schedule and let yourself evolve things from there without trying to force the situation. There's as much to learn from the feeling of giving up as there is from the feeling of flow, productivity, or success if you pay attention to it.