Excellent answers guys, I was thinking the burden of the ring, I've just been on isolation so watched all 6 in a couple days.
Poor Bilbo.
Particularly liked this but am disturbed as fuck:
either he was happily married to Thorin, or (female Bilbo re-writes) had an unhappy marriage to Thorin, LTB, and vowed "never again". There's a reason Hobbit fanfiction doesn't float my boat