clearly not everybody's experience.
And deserve what exactly? It's unkind, it's morally very wrong, but it's not that important.
If there was karma.. what about the ones who abuse their kids, abuse their wives? (sorry but it's more often the husband in these scenario). If people got "what they deserve" or what you think they deserve, something would happen to all the ones who stay married, don't cheat, but treat their wife like crap, leave her with all the mental and physical load, don't support her ever, keep their full time job, their hobbies, their evenings and weekends off, their night sleep. Meanwhile, their wives are left in tears, completely overwhelmed and unappreciated, and stuck because they have given up pretty much everything to take care of the family.
So no, I don't think starting a new relationship a bit too early is the worst thing in the world, and I don't buy for a second there's a "karma" attached to it.
"Cheaters" and cyclists seem pretty happy generally