I looked at some of the work by Noam Toran - Accessories for Lonely Man. His work made me think about the smaller things in life that a person can miss when it is suddenly gone.
Chest Hair Curler
Shared Cigarette
As well as the advice book, I thought about things that may be beneficial to mood. People often comfort eat when they are feeling low, but putting in a whole store of food wouldn't be practical so I tried to cut it down. Some foods are proven to make you happier so I searched for foods which release endorphins and found that the foods which could last a while in a box and still release a decent amount of endorphins are chocolate and nuts. using this information I decided to put my favourite chocolate bar (toffee crisp) and cashew nuts in my apocalypse time capsule.
I tried to think of activities to put in the box that would take my mind off feeling lonely or depressed. I looked into activities that can do this and came across a theory of 'Flow Activities' that can engage a person so much that it seems like no time at all has passed when in actuality hours could have passed. Activities like this can include playing games consoles, sports and knitting. Games consoles would be impractical and I don't know how to knit, so I decided to put a deck of cards in the box as it provides several solo games and countless multiplayer games, just in case there were more survivors after the apocalypse.