Cheating is always a no-go in any situation. Granted your wife has flaws and she’s imperfect, and Julia from work is much more attractive, but cheating is the worst thing you can do.
When you love someone, all you think about is them. Chris Evans says from the movie ‘Before We Go’: “When you’re committed to somebody, you don’t allow yourself to find perfection in someone else.”
I don’t think anything else needs to be said. Chris nailed it! Cheating is the worst sin you can commit. Never do it no matter what the circumstances. If you don’t find yourself attracted to your partner anymore, just tell them. This would be better than going behind their backs.