How do I deal with this unfairness 😒

The father of my 2 kids likes to act, pretend and talk as if he is a good father but he doesn't see them,make time for them or help me support them emotionally, physically or financially. He still tries to ruin my life, lie about me and blame me for him being a deadbeat, which is why he is now blocked on everything and I'm learning to ignore that bs as hard as it is. Most days I'm fine about it, but on my hard days I feel so down and out about how unfair it is that he gets to live life how he chooses, no responsibility, has a good job and keeps all his pay, doesn't need to work his life around kids, doesn't need to plan out when he can have free time, but yet here I am drowning in responsibilities and doing both my job and his. I love my kids, having them with me and being their mum, but on the days I struggle I can't help but feel defeated on the unfairness of this situation and it really sends me in a spiral. How do I learn to deal with these emotions, I'm trying, I really am, but there's only so much I can take 😢