Some idioms with "keep"

In keeping with = as appropriate e.g. In keeping with the company policy, all employees should wear a uniform.
Keep an eye on/keep tabs on = watch careful e.g. Keep an eye on him. I don’t trust him at all.
Keep a straight face = try not to laugh e.g. I found her answers to the interview questions really funny but I had to keep a straight face.

Keep at it = don't give up e.g. We has difficulties in the beginning but we kept at it and finally managed to build a successful business.
Keep going = continue e.g. The athlete was tired but kept going till the end.
Keep in touch = keep communicating e.g. Good luck with your new job. Keep in touch.
Keep it to yourself = do not tell anyone e.g. So now you know my secret but please keep it to yourself.
Keep one’s fingers crossed = wish for success e.g. I’m keeping my fingers crossed for my daughter who has exams today.
Keep one’s word = keep a promise e.g. They kept their promise and gave us free tickets to the football match.
Keep up with = maintain the same rate of progress e.g. It’s difficult to keep up with all the changes in technology.
You can keep it = I don’t want it! e.g. I don’t need the book. You can keep it.
Keep a low profile = remain unnoticeable e.g. It feels like she doesn’t even work here as she keeps a low profile.
Keep one’s options open = remain open to other suggestions e.g. I’ve had a job offer but I don’t think I’ll accept it as I want to keep my options open.