No is a complete sentence.

Saying no is a powerful choice.

Saying it without explanation or justification,
quietly without shame or guilt, (to yourself or to others)
frees up time, 
clarifies your priorities and 
reminds you that you’re the one in charge of your reactions to situations and people.

No. You won’t be making time to spend with people whose company you no longer enjoy.
No. You’re not going to ignore the pile of mail on the dining room table.
No. You won’t be sharing the bit of gossip you heard.

Saying no helps you clarify how you use your time,
where you spend your money, and
who gets your attention.
(All of which are in limited supply)

By saying No to ‘stuff’,
you give yourself the space and time  
to say Yes to to the people and activities you truly love and value.