Married unhappy - how to leave kids behind?

I am married for 12 years, have 2 kids 1- 3 yrs old. I fell in love with another woman, I never have cheated before , but just realised I made a mistake to choose this marriage, and live without love. I cannot abandon my kids.. they dont deserve to get hurt.. but I am not happy with my wife.. What to do now?? Anyone in the same shoes - resolved/unresolved?..