from Chapter 8 in 'Dekiru Nihongo' Intermediate / 『できる日本語中級』第八章より

8-4. 友達を慰めるときの表現

だいじょうぶ / Are you (feeling) all right?

たいへんだったね / I know what you went through. Oh, that’s terrible.

It’s nothing unusual.
It was just one of those things.

きにすることはないとおもうよ / Don’t let it get to you.

あんまりきにしちゃだめだよ / Don’t feel too bad.
You shouldn’t take this so seriously.

げんきだしてね・げんきだせよ / Keep your spirits up! 
Cheer up! Lighten up! You have to keep up your strength!
（出せ：命令形 / imperative）