Today’s word is something you won’t do if you really don’t like your Christmas present – and no, it’s not freuen. You’ll definitely fake that :) 

behalten

Literally, behalten  means  “to inflict holding on something” and that isn’t too far from the actual meaning to keep. Behalten isn’t as broad as to keep, though. It is limited to a sense of “not giving away/back” so it wouldn’t work for stuff like “keep me updated” and it also wouldn’t work if the focus is on “not throwing away”, like with bills or old pictures. For that context aufheben is the better pick.
behalten is also for in context of memories and secrets.
das Behältnis – a box or something similar
der Behälter – the container, containing unit

• Kann ich das Buch noch eine Woche behalten?
• Can I keep the book for another week?

• Maria kann nichts für sich behalten.
• Maria cannot keep anything to herself.

• (Das) kannst du behalten.
• (You can) keep it. (for good).

• Ich werde das im Auge behalten.
• I’ll keep an eye on that. 

By the way, behalten is directly related to to behold which once also meant to keep before it shifted focus toward” to keep in sight”.

If you want to try out some examples, or if you have questions just leave me a comment.