Sometimes things aren't easily done because we need to build up a momentum first. If you can do things consistently, you don't notice this because you almost always have that momentum. If you've been getting things done every day, it feels natural to be able to continue, or to go on and to more complicated projects and jobs.
However, when you've been lying in your bed for the past week/month, it feels incredibly difficult to imagine that you could just get up and start doing complicated or difficult tasks. Your confidence is low, your track record is hurting you, you feel it's a miracle if you manage to even get up and grab some food from the fridge.
But if one day you manage to feed yourself, and maybe even wash a dish, or do some sort of a chore, and the next day you manage to clean a little, or make an actual meal, and then the next you're doing your laundry and have fresh sheets on your bed, then you have gained some momentum, then you could actually go and socialize, or do a non-chore task. Doing multiple simple tasks ensures confidence to do a bigger one, granted that you didn't waste all of your energy doing the simple chores.
This why sometimes doing things related to a complicated project, without doing the major things, can help, because just by doing simpler tasks you're gathering confidence and momentum, you're building up to a place where it no longer feels so unbelievable that you could do something complicated that takes skill and brainpower.
And sometimes, when you're chronically ill, you start building up your momentum and then your state worsens and you end up back in bed, your momentum interrupted and your confidence back at the bottom. It's difficult to get to a place where you have momentum, if you have no energy to build it. Nobody could just get out of bed and immediately preform miracles, we need to be able to do simple things first, small and easy tasks first, until we're ready to try for something more scary. Doing things makes doing other things less scary, and more possible, but if you're constantly interrupted, it's a struggle to convince yourself that one day you'll be able to do it.
