I once heard this George Bernard Shaw quote used on a commercial and it has always stuck with me.
The image it paints is so ridiculous that its truth quickly becomes obvious.
Always beware of those willing to tell you what cannot be accomplished, especially when your gut tells you it can be.
Far better to be the one achieving when others say you can’t, than to be the one saying it can’t be done while others are doing it.
I suppose this is exactly the trait we mean when we talk of an ‘entrepreneurial spirit.'