Say there is a special type of cake, very delicious, one of a kind, and is to be given to you now or ten years from now. If you have it now, you can't have it later. If you have it later, you can't have it now. Would you have it now or 10 years from now? I argue that enjoying the cake now would imply that you get 10 extra years of good memories. Hence now is better than later in terms of utility. This might be a bit simplified as memories do fade over time, but still, delaying gratification only means overall less memories.