One of my personal commandments is to say yes. So isn't a Pep Talk on saying no counter-intuitive?
Not at all. The only way to be able to say yes more often without stressing yourself out is to also say no more often.
If you need more "no" in your life, here are a few items to consider:
Clarify what's important to you. One of the most powerful sayings I've heard and internalized is, "When values are clear decisions are easy." Knowing your values and priorities can help you decide if you should say yes or no. And even though you don't owe anyone an explanation ("No" is a complete sentence), it does make it much easier to say no when you can talk about what you're working on. Early this week, I responded to a request with, "I am going to decline because I'm putting any extra time I have into building my side business." Other examples include "I function better the next day if I'm in bed by 10:30 so I'm going to head home" or "I'm committed to being home with my family four weeknights each week so I can't commit to meeting every Tuesday."
Consider the impact. I've learned this lesson the hard way by immediately saying yes to an invitation to go out or to participate in a project, and only then thinking about the impact of my decision on my family. Then I have to reorganize schedules, ask for forgiveness, or turn that yes into a no. Yuck. I'm trying to get better at thinking about the impact if I say yes and the impact if I say no before I answer, and it has helped me make better decisions. And if I get a request from someone with whom I don't enjoy working, I recognize that I'll probably end up complaining about the person while working on the project, and that leads me to an easy no. (I'm reminded of the advice to predict the predictable.)
Put it in perspective. Many of us tend to feel really guilty about saying no, but often, it's not that big of a deal. I used to accept every baked good someone offered me, but I've learned saying, "Those blueberry muffins look delicious but I'm going to pass" feels much more comfortable than eating something I don't love and feeling bad about the calories. I remember working on this with a therapist when a friend asked me to go see a re-release of her all-time favorite movie. I knew she really wanted to go and might not be able to find someone else, but I also recognized it wasn't my job to be the hero and going to the movie wasn't a priority for me. I said no. Not only did the world not crash down around me, my decision didn't really seem to hurt her at all. (Note: if the person you're saying no to lays on a pretty big guilt trip, you may need to work on distancing yourself from that individual.)
Take no for an answer. If you want the people around you to get used to you saying no, you need to be comfortable accepting a no from others. A surefire way to harm relationships is to stand up for your own boundaries with no regard for the boundaries of others. If someone declines an offer or request, don't require an explanation or put on extra pressure. A simple "Okay, thanks for considering it" or "I respect your decision" can go a long way.
You always have a choice about how you respond to a situation or request. Sometimes the best choice is to say no.