Continuity mistake: In the very first episode, Josef mentions that Mick is ninety, and later on in the episode, he mentions that it's been sixty years since he felt the touch of another human being, or something like that, meaning he was turned in his thirties. Yet in episode three, I believe, he tells Beth that he'll be eighty-five in November.
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