(1) Watch out!
You should be more careful.
That car came out of nowhere. あの車、いきなり出てきたでしょう。
(2) Stop complaining so much.
Think of all of blessings you have.
Things are better than you think. 状況は君が思っているよりいいんだからさ。
(3) You seem to be looking for something.
Why don't you tell me what it is? 何なのか教えてくれる？
Maybe I can help you.