How do you motivate yourself? How do you pick yourself up when discouraged?

I live in a world of chaos and there are not enough hours in the day to do everything I need to. I work full time, I’m a single mom, and I am one credit hour short of going to school full time. It may not sound like a lot, but it is. Sometimes I just get so discouraged and want to give up. I hate making anything less than a B in school, so when I make a C I get really down on myself. I know I’m doing the best I can, but it’s just so hard to study like I want and need to. I love school and I know if circumstances were better I would get the grades I want. It just gets really hard sometimes and it makes me want to give up because I am just not happy with myself. I know it’s part of life, but there are just so many things I wish I could fix. I wish I didn’t loose time with my son. I am so scared of missing out on things with him. Any pearls of wisdom, oh wise flutherians?