I may be a big baby, but I have relatively small batteries. I seem to run out of juice quickly when I’m active. Tummy time and interactive play drain my batteries very quickly. The result is groggy and lethargic movement with very tired grunting. But you can tell that I’m growing up because I don’t get too fussy too often anymore. I just slow down and take things easy until I recharge, either through feeding or sleep.