Then you get to be grandparent - the person who is allowed to say 'I can't babysit tonight - I'm off {insert something that they find obtuse and pointless}', spoil the little snot-nose silly and HAND IT BACK, and wait, remember the grandchild will be a teenager in time...
Drink the brandy and start plotting - in a few years you get to start asking where the grandkids are - and that'll make the (granted older) teenager run for the hills (assuming you have taught them enough that they aren't the ones who make that mistake - in which case teenage revenge just comes quicker). Work out your 'spoiling' tactics - too many trips to Disney? That expensive thingy that their parents don't want them to have (such as a love of real books - think how hard storing paper is?), the masses of hand knitting they have to get the grandchild to wear at least long enough to pose for photos... You have options

Good luck in surviving the next few years - you can always do what my Mum did. I made the mistake of complaining laundry took soooooo long to get back...I found out the next Sunday afternoon she had stopped doing my laundry (I had asked where my school uniform was - my Dad was ironing my brothers' and not mine). I had an interesting afternoon working out the washing machine etc before school the next day.