My fiance and I are having a really hard time. He works his butt off so me and our 2 kids have what…

My fiance and I are having a really hard time. He works his butt off so me and our 2 kids have what we need and I'm not happy at all.. for some reason I don't appreciate him and I never tell him thank you for working and helping me with the kids so I can get to sleep.. what is wrong with me? How can I fix myself? How can I stop all the fighting and heart break that happens every day? Can anyone help me because going to therapy isn't doing shit...