Dic: get your mind around something

• I still can't get my mind around the strange things she said that night.

to succeed in understanding something difficult or strange (usually negative).

... Cambridge Idioms Dictionary

Cf. get your arms around something: to feel confident that you have a good understanding of something that is complicated.

• There are so many different aspects of the energy situation that it's hard to get your arms around it.

... Cambridge Dictionary of American Idioms,

http://idioms.thefreedictionary.com/around