Why does something has to come and ruin everything when you are finally trying to be happy and be a…

Why does something has to come and ruin everything when you are finally trying to be happy and be a good parent?

I have been trying so hard to be a good mother i do everything and anything for my kids to see them happy, healthy, everything but it always seems like everything i do i do it wrong they dont see that i am trying to become a better person for them but something always has to happen i just dont know what else to do i just wanna sit here and cry all day... everything reminds me of them...last night my neighbors baby was crying and it was like 4 in the morning when that’s around the time my 1 year old wakes and i just couldn’t help it but cry i missed waking up in the middle of the night to feed him and put him on my chest... last night when i gave them to their father and his wife i just felt like my heart broke into a million peaces like i know they gonna be okay but i just want them to be with me they deserve to be with me idk what else to do