[c_moscardi]

To me, the interesting bit here is that you have to be honest with yourself about your limits as well - and in particular, be very good about understanding those limits.

I think in this instance, ethics and economic incentives align - your expertise is part of your value-prop to clients, and having a good grasp of your limits makes you substantially more valuable. You get things done on-time, with clear expectations set, and do a prompt and thorough job providing what you're being paid for.

Personally, as a natural optimist, one thing I need to be especially careful about is not saying "yeah that's doable!" and setting expectations too high - it can potentially lead to a messy situation. That said, one of my favorite parts of freelancing is that I get confronted with new, unique challenges that I've never dealt with before - there's a balance to be struck here.