Cupids don't do feelings - they handle them, they stir them up and stimulate them and get them going in the right places between the right people, but you'll never catch an angel with both wings on his back and his heart in his hands. Love wasn't made for them to have, it was made for them to give. So, reason number 1 as to why Soonyoung hates being a Cupid: he's no good at it, fails all his missions. And reason number 2: he doesn't know how to not fall in love with his target. Even if Jihoon wasn't head over heels for someone else, Soonyoung couldn't have him. That's a problem.