If I really want to do xyz, I will move heaven and earth to find all the pqr I need.
If I pretend I can't do xyz because I don't have any pqr, people will start trying to help me find pqr, and then I will either end up sulking, or doing something that I didn't want to do in the first place.
There is no need to feel guilty about not doing xyz. It's not because I'm weak. It's not because I'm lazy. It's because I don't want to.
It is absolutely fine not to want to do things -- even things that seem fun, or are good for my body or my soul. I do not need an excuse. All I need to do is to be honest in the first place.