I: Ignore negative vibes
Stay away from Debbie Downer and Ned the Naysayer. They will only bring you down. And it doesn't do any good to gripe endlessly. If you have a complaint about something, be positive and proactive, don't act like a victim.
J: Just say "No way"
Stop being such a people-pleaser! They don't appreciate it and it's killing you! Okay, maybe that's a bit dramatic, but you get the picture.
If you're the one co-workers constantly call on to do extra work, start declining their invitations (politely, of course).