It will kill your emotions. You watch as friends and loved ones come and go, yet you can never be with them as you know you will stay the same forever. So after 1374 years of living, 752 relationships, 53 weddings, 97 children, you sit down and evaluate your life as you watch son's daughter's granddaughter's niece's son grow up and go to university, just like you watched all of your other children do so. You die inside of sadness, basically
Papyrus will get mad at you for not eating his spaghetti, since I told you you could choke on it, so he calls Undyne and she murders you since you chose genocide, you heartless monster.
Your brain is overloaded by the bananabanana power, so you descend into madness and insanity. You suddenly turn into a banana and people eat you. "Nom nom nom" is the last thing you hear as they slowly chew your banana ears.