It's a two-edged sword, the hobby is.
For me, it started when my kids were small and sleeping with mom, and mom enjoying her kids more than myself. I was frustrated and angry all the time, pent up. Working ridiculous hours in my own business, traveling, and when I finally arrived home, a loving family with SO and kids, but no quality love-making anymore. I was the respected and loved provider.
Out of desperation, finally got the courage up to go out and find a girl. It was great. I came back home happy. Wonderful afterglow. Didn't really need the SO anymore for sex. She provided a beautiful warm home, being a stay-at-home wife/mother. Decided I would have a new exciting life on the outside and at the same time provide for my family. Throw in the obligatory romp which is all the SO wanted anyway.
She knew, but kept quiet and respected our new roles.
The negative is that we lost phsysical closeness. The love and commitment is still there but the contact is gone. We learned to live together and would never leave each other because there is a strong bond of true love, being married young and innocent, us against the world and wanting to be there together for our children who are adults now. Not to mention her incredible loyalty and forebearance.
I have my sexual freedom on the outside. But, still, a gnawing feeling that I could have done better for my SO. Plenty of guilt. I am seeking out a way to somehow turn it around. Where there is a will, there is a way.