Bitter people are often just people who said yes way too many times.

Bitterness usually starts as accommodation. Each yes seemed reasonable on its own and cost a little more than it looked like it would, and the unpaid total collects somewhere until it surfaces as sourness. What reads as a hard character is often a long record of declines that never got said.

Rather than judging that in somebody else, check your own ledger. Where are you agreeing while quietly keeping score? Say one of those nos out loud this week, before it has time to turn into the other thing.