Skye, feeling tired and overwhelmed is hard, it usually precedes tears and a break down for me. To avoid feeling overwhelmed may be you could try to shrink that big picture you're looking at. Instead of keeping the whole house clean, just start with one room, clean that one room and when you're done try and allow yourself to feel good about what you have accomplished. Doing something may not be doing everything, but that's ok because it's not doing nothing.
"I try so hard to get my daughter to preschool on time but I am always five minutes late." If you're getting her to preschool always five minutes late than you are still getting her to preschool at the same time everyday, which is an accomplishment. I'm always late getting places, I try to set my clocks at home ahead 10 minutes so I'm better at being on time.
Sometimes when everything gets overwhelming it can be better to focus on one issue at a time when you're trying to make changes. I hope you're feeling better soon.