Is it true that we have to go though pain to grow?

I’ve been hurt so many times, disappointed and betrayed. A boy broke my heart because he didn’t like me back and also because I’m tall. One of my best friends changed for the world and she posted about me on the inter and people call me ugly names and blocked me.
My half sister told me, “I know it hurts to go though rejection and bad situations BUT that helps you grow as a person. You have to go though pain, and be uncomfortable to grow and sometimes you HAVE to go though bad situations to appreciate the good. If you don’t and if the world was all butterflies and rainbows all the time, how are you going to know how to appreciate the good times we have? And how will you know what bad is if you are just used to life with just happiness and rainbows? I know it sounds harsh and uncomfortable but it’s the truth. You HAVE to get hurt to grow. Nobody likes to get hurt but it makes you a stronger person. If you never been thought pain, then you won’t grow as a person. See what I’m saying? Just like when someone tells you the ugly truth in your face to see what mess you’re in, you will be a better person.”
So going though pain is a GOOD thing? I guess bad things are good.
My sister is 33, OLD. How would she know a teen girls life?