I begged my former boss for my job back and make another contract, but they refused!

I know I’ve been grieving about my dads death in March. I went back to work two weeks later because I was grieving so much. So I was doing my job and I worked with kids. My first three weeks I worked there, the teacher had to talk to me bluntly because I wasn’t being firm enough with the students and I let them do whatever they want and the other teachers have seen it and they’ve discussed about that I not doing my job as a staff. They said I’m not being fair to other students just because I work one on one with an autistic girl. If I keep this up, they’re not going to want me to come back to work for them and revolt my contract. They’re allowed to do that.
One time a girl scratched another girls face bad. The assistant scolded at me that I needed to be on it and I just stood there and let it happened. That was before my loss. Another student got hurt by jumping off the table and hurt himself. We’ll she shouldn’t have got on the table. I got called out for letting him jump off the table and he got injured and lying about it. The principal had a stern talk with me and they revolt my contact and let me go. I told them I went through a loss but they said it’s understandable it’s difficult but lying about a child getting injured and not being close to the table is not tolerated and they fired me.
I told them I’ll do better next time but they refused. What do I do?