Set your own agenda. It creates consistency for others and is habit forming. If you aren’t on your own agenda then you are on someone else’s. Stick to your plan.
You’ll find yourself saying no more than yes…that means it’s working.
Be careful of maybes. A quick no is better than a slow maybe and clears the way for a yes.
markbartels.org 
Also, people respect you more for a genuine “no” more than half-hearted “yes”. A no from you means they can seek out a genuine yes from someone else whose agenda is better aligned.