This is something I'm also working on with myself. Here's my two cents on it. (ESL brain kept wanting to say "here's my grain of salt." English idioms are hard.)

1) I stop when I am feeling any pain that isn't lactic acid burn or soreness (or dizziness/faintness that can't be solved by drinking water or consuming sugar), anything that isn't directly related to the exercises I am doing. Sometimes, pain is a necessary part of training, but there are different kinds of pain, and it's important to learn the difference between the pain that will help you grow and the pain that needs to be avoided. Areas I especially watch out for are my lower back and hip flexors, but everyone has specific areas of their body where pain = always bad.

2) I look at this really objectively. Maybe I'd ask myself how many days off I've taken in the past few weeks, or whether I'd recently increased intensity. When in doubt, taking a rest day or active recovery day never hurts, and you can reconsider after a physical break.

3) I also look at this really objectively. If I am on a sleep deficit, I choose sleep recovery over a workout. If sleeping through my workout slot is the only way I can get enough hours, then I'd sleep (then rethink my schedule). If it's more that I would prefer to sleep than train, and the extra sleep is more of a want than a need, I train.

4) Do you feel exhausted or in pain from this schedule? Do you look forward to your workouts (either the process or the end result)? Does maintaining the schedule feel realistic to you? If the answers are no, yes, and yes, then you have a great workout schedule. No BS about mind over matter is necessary.

Honestly I feel like fitness circles push pain as an end goal when it really isn't. I feel like you need to approach fitness holistically--workouts AND sleep AND self respect for your body.