Clark: Remind me to thank my mom.
Before Kara, l had no idea
what she and my dad went through.

Lana: You turned out well. With his heart in the right place?
Clark, don't you think
you're being a little hard on Kara?
Lana, l'm trying to help her.
Kara didn't grow up here. She has no idea what could happen
if someone saw her use her abilities.
Right now, she's about a fireball away
from lighting up the whole town.
She's barely not setting on fire the town?
Lana: This is how you've had to live
your whole life, isn't it? Hiding.

Clark: No, adjusting. And, sooner or later, Kara's gotta figure out
how to do the same thing.

Lana: Clark, your parents trusted you enough
to live your life and find that balance Adjusting? on your own.
Don't you think Kara deserves the same chance?
You don't have to be too hard on yourself. Stop overreacting?
"turned out well" - he's a good/nice/successful person. Regardless of whatever problems his parents had, it didn't adversely affect his development.
fireball - Yes, she's very close to setting the town on fire.
Find balance - finding ways to cope with both living a normal life and having superpowers. We often talk about finding "balance in life," which usually means not letting one part of life, such as a job, dominate everything else.
Don't be too hard on yourself - don't feel so much guilt, stop reproaching yourself. Another way to put it is "Stop beating yourself up."
Thank you, Delmobile!