For me it's people.
Other than partner and kids , I have 2 family members, Mum and sister, and we live so far apart we rarely speak or meet up. We have nothing in common.
I have 3 friends I see every month or so.
I'm envious of people that come from big loving families.
I can go for days without speaking to anyone outside of my household. I used to be quite a sociable person. Now I have no confidence.
Loneliness sucks.