What Do You Wish You Could Be?

Do you have a dream job? If you could have any career in the world what would it be?Or are you already living your dream life?

Do you notice how "could" is used in this question? The modal verb "could" has many functions. One is to show that there might be a possibility of something happening, but there is also a possibility that it might not be possible and will not happen.
Example: This rainy weather could ruin our road trip today.
We don't know if it will ruin it 100% but there is a chance and probability.

Whereas the modal verb "can" leaves very little possibility or chance. It's almost certain.
Example: I can speak Spanish.
It is certain that I can speak Spanish.