Can I contribute too much?
It's crazy to think you can "save too much," but if you've exceeded the max HSA contribution, these funds must be removed from your HSA before the tax filing deadline — usually everyone's favorite day, April 15. If you don't, these excess funds become part of your taxable income. That doesn't seem so bad, until you realize they are subject to a 6% tax, which compounds each year you don't pay.
So, if you've gone over for the year, and still want that money set aside for your HSA, simply move that money to another account, then reinvest it the following plan year.