Plot hole: I believe in the very first episode, during the flashback when Mick remembers rescuing Beth and killing Coraline, we see him stab her with a wooden stake, which is supposed to paralyze a vampire, as said in the "Dr. Feel Good" episode. However when Mick looks back with Beth in his arms, Coraline suddenly gets up and watches him leave while burning to "death." This is simply not possible; in the "Dr. Feel Good" episode, Mick could not release the stake himself and asked Beth to do it. This also happened in the episode when Josef was staked by the hit man that was hired to kill him, (in the episode where we meet the woman, Sarah I believe, that he accidentally put into a coma after attempting to turn her). Again, Josef was unable to remove the stake himself and Mick had to do it for him, so there is absolutely no way Coraline would be watching Mick and Beth leave; she would still be on the ground possibly burning to death.
Continuity mistake: When we see Coraline in Mick's vision of when he was taking her dress off at a party, her tattoo is under one of her shoulders (I think it was her left one) but later on in the series we see Morgan/Coraline wipe off the make-up on where her tattoo is...on the opposite side.
Answer: I don't think he actually meant his life would be unbearable. I just think he meant that he wouldn't be able to live with himself, figuratively speaking, if he was to feed off the woman he loved. Expecially after spending 22 years protecting her from danger, he would be the one to cause her pain.
Rin823