When you're a kid you think that you're immortal and take stupid risks. A little bit older and you love life just as much, but realise that it might not last forever. Add in some family responsibilities ans staying alive becomes very important.
At this stage of life after losing one of the key things that makes life worth living you've lost the love of life and incentive to live at all costs, so although you realise that you are mortal you can to some extent go back to behaving like a kid. The difference is that the kid is convinced that he can't die. We know that We can, but don't care.