Really sorry to hear you are feeling this way right now. You might not be able to see it but that voice saying "tomorrow", "tomorrow I'll do it, tomorrow I'll be a good person, tomorrow I'll shower and clean my house" is
you coping as best you can at this moment. If saying "tomorrow" helps you get through today then you are doing a good job. There's a quote I like about hope not being a sign of weakness, but a gift we give to ourselves, and it is a sign of strength. I don't know if that's something you relate to but your message reminded me of it.
I'm very sorry about your loss, it sounds incredibly difficult. I don't think you are mad. Grief can make us a bit crazy sometimes but it's understandable when something so big and life changing happens.
You mentioned looking for ways to help yourself, I'm wondering if something you could do would be to ask help from others? Maybe you have a friend who also wants to spend more time at the gym? (and maybe something easier like once or twice a week to start) Or someone who would enjoy walking the dog with/for you? I can't have a dog at the moment but I would love the chance to hang out with a dog
Sometimes we aren't aware of what help people are happy to give until we ask.
I hope things feel better soon!
Kindest regards x