So most teachers have way too many bags and have back and shoulder problems/pains from the amount of things that we take home nightly. Then we forget the things we need to get it done.
Here is a suggestion: Invest in a GOOD book bag - yes like the kids. Not on wheels (hard to lift), not a messenger bag (will cause neck and shoulder pain), but a GOOD solid book bag with straps, pockets, and space for a laptop.
Try this and see if you can't get more things home and feel less pain in the process. Don't over stuff - that will still cause the back and neck pains.