Serving as the executor of an estate can mean taking responsibility for a large number of different, difficult tasks. For example, you will likely need to make an inventory of physical possessions and place a value on each item. You will need to advise creditors and service providers of the death of the testator and arrange for the transfer of services while also paying any final bills from the proceeds of the estate.
Beyond that, you also have an obligation to meet the tax liability for both the deceased party and their estate. If you make a mistake in the administration of the estate, you or beneficiaries from the estate could wind up legally or financially responsible for those errors in the future.