When you already have a partner and having feels for another girl it's lust. I had an idiot for a friend once, he's married with two kids and was telling me he felt hurt being rejected by the girl he was having an affair with. What kind of person feels hurt being rejected when he's already married with two kids? The marriage itself isn't even falling apart, he's just egotistical because he thinks that his life should be easy without thinking of the consequences to others.
https://experteditor.com.au/blog/thi...-realizing-it/
Maybe Sean_lee should read this article and re-evaluate his life choices. I grew up accepting life's hardships because I didn't want the choice of suicide. I also understand that if I finally marry M one day our life isn't going to be rosy and filled with happy endings every day, but when evaluating M's personality compared to all my exes she's the one I'd rather live with in both ups and downs. Don't be surprised at how many people choose suicide as a way out of life, many successful rockstars ended their life because they can't find the satisfaction they needed even when they're banging groupies on a daily basis.
If you want to leave your partner, don't leave her just because you have a "side chick". You need to do lots of inner works before you determine that the both of you are no longer compatible with each other, and if you have kids you'll also need to think of their welfare instead of selfishly thinking of your own.