It's not very uncommon to think saying NO creates a negative impact on our life. And when we talk about personal development, mindfulness and giving more time to learn, it seems quite opposite to say NO more often. But we have to understand saying NO doesn't mean denial, it means choosing something better for us.
As an important practice to adding more space for ourselves, we have to learn how to say NO without not offending others. People pressure or social norms will always try to take us down. But saying no means adding more space to life, setting boundaries, slow down and focus on what we need for our best.
You will find many who rush all day to meet others' needs, expectations. Their schedule is full of many things which don't actively add any value in their life. Don't make yourself that person. Give a good look at your life and make time for you. Yeah, I'm not opposing helping others. But we sometimes choose to make our life complicated with stuff that doesn't make any sense. Take care of your life and make some white space in your schedule.
Every time we say yes to something, we choose to have less time for us. It may sound selfish to you. But don't generalize. Just think this way, attending a party can't be more important to take personal care or losing the time to study. But we have to choose carefully whether our NO is making us disconnected from everyone.
Make sure your NO and Yes aline with your priorities of life, goal, and value. That's when it will be wise to say No more often!