The unexpected job offer. The side project that may be outside our scope but promises easy cash. An opportunity that offers "great upside," or a "chance to build our portfolio/resume," but isn't something we're passionate about or it won't pay the bills.
What's your "one thing?" The thing that makes you different? The thing that you are not only passionate about but is also something you can be the best at? Why should anyone choose you over all the other options out there?
These are the questions you should be asking yourself.
Don't ask "how can I say no?" Ask "does this 'thing' add value to my 'one' thing?"
1) If we say yes now to the easy opportunity just because it offers a quick reward, we run the risk of having to later say no to more meaningful ones.
2) If it's not a clear yes, then it's a clear no.