What do banks look for when checking your spending habits for a mortgage assessment?

I'm looking at buying a house in about 4-5 months and wondering what sort of "spending habits" I should get into so that my bank statements look as good as possible for the bank. From talking to friends who have gotten mortgages some have said the banks go through their statements with a fine tooth comb to see how much they spend on dining out, alcohol, gambling, etc.

Some background info, i'm a single guy, mid 30s, and just moved back in with my parents to help save money for the deposit. I'm lucky that I don't have to pay any living costs so have very minimal expenses atm.

EDIT: thanks for all the replies👍