Back-to-school day was so hard for me before we had M, when we were TTC. Everyone was on Facebook, sharing pictures and love for their kids. Which is awesome of them to do. But it can be hard if you're the one without a kid and you'd give anything to not be in that place.
So to the ones who are sad today, I see you. God sees you. You're not forgotten. Far from it. Whether you're trying and trying to get pregnant, you're recovering from loss (yesterday or a decade ago), or circumstances separate you from your kids, you're not alone.
If you can't take seeing all the back-to-school stuff online, do yourself a favor and don't get online. There's nothing wrong with the posts being there, and there's equally nothing wrong with you if you can't handle seeing them. Instead, do something for yourself today that will feed your soul and build you up. Spend time resting in God. Listen to uplifting music. Workout. Make yourself a healthy, satisfying meal.