“Sometimes the key to making progress is to take that very first step, then you start your journey.  You hope for the best, and you stick with it. Day in, day out. Even if you’re tired, even if you wanna walk away, you don’t because you are a pioneer. But nobody ever said it’d be easy.” 

- Meredith Grey in Grey's Anatomy

Yes you can say no. You can say no when you’ve said yes all your life.

You deserve to live your life. Live for yourself.

You only have one life. You can do whatever it is you want for yourself.

There is nothing wrong with living first for yourself.
For only when you are whole within yourself, and love yourself, can you fully love another. 

Grey's Anatomy

Dr. Bailey: I took pause.
Dr Yang: You paused? 
Dr. Bailey: I paused.
Dr. Bailey: I paused a very long time.
Dr. Bailey: So why did? I sat up one night, middle of the night and I knew I could do this.
Dr. Bailey: I still don't know how I'm gonna do this, but I knew I could do it.
Dr. Bailey: You just have to know.
Dr. Bailey: And when you don't know, then no one can fault you for it.
Dr. Bailey: You do what you can, when you can, while you can.
Dr. Bailey: And when you can't, you can't.

We can always look back in our lives and think that we could have done certain things better but the fact is.. it was the best we could do at that point in time with the limited experience, knowledge and understanding that we have. so we should learn to not keep faulting ourselves for the things we did in the past but look forward to see how we could do better in future.