Verb
contemplate - To spend time considering a possible future action, or to consider one particular thing for a long time in a serious and quiet way.

Now that Angela had graduated from college, she had to contemplate whether to get a job or get a more advanced degree.
simmer - To heat a liquid, usually a stew or soup, just below the boiling point, allowing it to cook slowly; or to stay in a slow, controlled state of progress or tension, often before a larger event or change occurs.

He was simmering with anger, but he kept it inside and didn't say out loud what he was thinking and feeling.