Determined Underachievers Lucy’s point about adults being uncomfortable with things they can’t do well is true. Youngsters ‘learn things for a living’ as Phil Gay once said, but as they grow older they give up what they aren’t good at and only do things they are (reasonably) good at. For most people the last physical skill they learn is driving, in their late teens.
I remember being very frustrated and disappointed trying to learn hang gliding in my mid 30s. I expected to to be as natural as cycling but it wasn’t and I kept doing the wrong things. In the end I gave up (probably a good thing given the accident rate).
In your case I think you need to unpack what’s behind ‘I can’t do it’, which could mean two different things.
It could be if it is a simple statement that the keel ant skill/knowledge/knack is absent then the way forward is to work with them to identify what is missing and try to find explanations and exercises that could help to fill them.
Alternatively it might be an escape message, like the day I stood at the top of the hill without the courage to make a flight because I didn’t have confidence in my ability to fly safely. In your case it’s obviously not as safety fear, since he/she is willing to ring, but it could be a fear of failing to make whatever improvement step you are asking to be attempted because it feels impossible. If that is so you need to find out why and try to find a way round it or to break it down.
Either way with an adult you need to work together to find out what the problem really is. What is ‘it’ that can’t be done? Then explore the problem and find ways round it. You might need to come at it from different directions rather than straight on.
Good luck.