Go back into your childhood by making something to eat that you haven't had in a long while.
It works best if it is something that you often ate as a child. It sounds terribly silly but it works. Think of something you haven't had since you were a kid then make it!
What did it for me? Grilled cheese sandwich. As an adult i haven't had one in ages. I made one for kicks and it instantly made me feel like a kid again. Anything works.
If you have kids then you may already do this but the rest of you should try it!
What food do you remember eating as a child that you no longer eat?