I'm not going to help my friend
Why won't you help them?
I'm running out of time, I still have to do things for myself.
Have you told them that you are busy? Friends are expected to help out when they can.
I just can't help with those things. I'm tired and need a break.
If that is the reason you can't help, I think you should tell them. They should be really understanding and accepting if they are true friends.