Yes is easier to say than no.
How many times have you said yes when you meant no? Face it, there are only so many hours in a day and if at some point you don't say no, you'll never get ahead (or get any sleep!).
When my sons were younger, I was at the top of the volunteer list (translation: sucker).
Whenever someone called me to help with an event, class project or anything else to do with school, I said yes.
I did the same thing with two professional associations I was in.
One day I had a revelation.
I was spending more time volunteering my time than growing my business.
I'm all for helping others but eventually you have to say no.
Before you say yes, consider a few things I finally learned:

• Be selfish with your time.
  When you say yes to one thing, often you'll have to say no to something more enjoyable.
  Look at your schedule and determine if you really have time to tackle one more project.
  If not, be honest, be direct and say no.
  Something I've finally started telling people is that I could say yes and do the job halfway or say no and let someone do it right.
  That always works.
  
• When there's no more room left on your plate, let the person know that you're too busy to meet his or her request, then recommend someone else for the task.
  But keep in mind that whomever you recommend is a reflection on you.
  Don't suggest someone unless you have first-hand knowledge of his or her capabilities.
  
• If you know you won't be able to meet your client's deadline, discuss a more realistic date.
  If you can't compromise, be diplomatic and turn down the project.
  Some clients will gladly wait for you to begin working on their project.
  

You can't do everything but when you learn to say no, you can do more of the things you enjoy doing.