My Apple Watch won’t hold a charge for more than a few hours. What to do?

If It is an older watch, then the battery is most likely just getting older and can’t physically hold as much of a charge as it used to.

If this is the case, I would look into replacing your watches battery.

watch Service Pricing - Apple Support

If your battery health is approx 80% or thereabouts,then it is recommended that you replace the battery.