I hate myself for not leaving my job

I feel so much dread every day and I cannot stand the thought of going to work. I really loved my job at a small business and then out of nowhere we lost some really great staff and I was left holding it all on my shoulders. I felt like I was failing because I was doing so much and was still so behind. I felt myself checking out and I am so disappointed in myself for that. Nothing was too hard, it was just a lot. I want to quit so bad but I feel obligated to stay because the owner and other staff have been so kind and supportive and I truly did love my job for 2 years. Everyone always tells me I am doing a good job but I know I am slacking so I feel even worse. It’s like I have senioritis and I don’t know how to just up and quit. I know I can. I know I should but I just feel so paralyzed. I even stepped down to part time but I just can’t push myself to officially quit. I feel like that bird trapped in the open cage. All I need to do is turn around and walk away but I can’t.