This post was written as part of the IBM for Midsize Business program, which provides midsize businesses with the tools, expertise and solutions they need to become engines of a smarter planet. It’s a leader’s job to say no.To be an effective leader, you have to say “no” to all of the opportunities that show up on your desk but aren’t aligned with your goals. Saying “yes” to all of the opportunities that might be interesting or might produce some result dilutes your efforts and makes reaching your real goals less likely. Saying “no” to small things makes room to say “yes” to bigger things.A leader has to say “no” to cultural mismatches, and the faster they do so the better their results. You can’t fear saying “no” to clients or customers who will drain your team, destroy morale, and change the culture of your company. And you can’t say “yes” to people who might produce some results for you as an employee while destroying the culture you are responsible for protecting.There will be times when you are are challenged to say “yes” to something that sits right on the border of ethical and unethical behavior. It doesn’t matter that the decision is legal, and it doesn’t matter that no one will ever find out, you have to say “no” to anything that will call into question your integrity. Your team won’t do what you tell them to do, they’ll do what they see you do. You have to say “no” to putting money above integrity.Saying “no” doesn’t make you popular. It isn’t easy to do, especially when you want to support the people you lead. But saying “no” to things that are out of alignment allow you to say “yes” to all of the interesting, creative ideas that are aligned with your goals.