Sometimes, of course, you have no choice but to say yes.

You are struggling to pay the bills or get established, for example. Or maybe it's a referral from a client you truly like and don't want to alienate.

But occasionally--and I'm not recommending that it should be more than that--no matter how nice it would be to have the money or how much you are intrigued by the project, you need to say no when someone offers to hire you.

Let's run through five potential reasons why, starting with the easiest one.

1. You cannot do a good job within the time available.

It could be because you think the client's deadline is not realistic, or you simply don't have the resources available to do the work in time. In cases like this, saying yes will just lead to an unhappy client and damage to your reputation. You don't need either one of those things. Just say no thank you.

2. The client is a MAJOR jerk.

"Client" and "difficult" are often synonyms. So just because it looks like they are going to be demanding is not, by itself, a reason to say no. But if the client is driving you nuts before you have the gig, there is no reason to think things are going to get better after you decide to work together. In situations like this saying no may be the right answer.

3. Time sucks

It is not always possible to see this one upfront, but sometimes you can. There are certain clients who are always going to take up substantially more time than they should. Giving people 10 percent, 20 percent or even 33 percent more attention than you budgeted for is fine. But 150 percent? Not so much. Another case where you want to say no.

4. It's not them. It's you.

By any objective measure, the client isn't a jerk, but they can push your buttons. Maybe they remind you of a client who was a major pain in the past. Maybe they remind you of your mother. Whatever the reason you need to be aware that they are making you uncomfortable. Maybe you can rise above it. But maybe you can't.

5. Opportunity cost

This could go a number of ways. The obvious one is that taking on the work would keep from doing something better, more interesting, more lucrative or whatever. But it could also include the fact that while the work you are being offered is high paying, it's "off your brand." It is not the sort of thing you want to be known for. It's another thing to think about before saying yes.

In any of these five situations, you may want to think about saying: "Thank you so much for the offer, but I don't think we're the right resource for you."