It's good to have a positive outlook, but it's also important to be realistic, and know when to move your energies elsewhere, I think.

I could set my mind to becoming a good orchestral composer, but all I'd be doing is wasting years of my life and a lot of money and effort, because I know I'm not at all creative in that way. My creative strengths lie elsewhere.

I could stick with it, and become at best a very derivative boring composer, but I wouldn't reach my dream or being a good one.

And I'd miss out on other dreams I could have been following that were more realistic and would bring me more happiness in the end, you know?

But yeah, you also have to weigh that against pushing yourself past your limits, because maybe you'll be great at something you wouldn't have expected!

I think in the end as with most things in life, it's about finding a balance between idealism and realism that works best for you :-)