我想去散散心 I want to have a walk to relieve myself. 我想陪他去散散心 I want to have a walk with him to relieve him.

Being preoccupied, you need to do something to chill and relief the cloudy issue in your mind. 散 is to loosen from intensity，to relief；心 refers to mood or notion in your heart。散心 is the same as meditation，clear up extra notions and relief the mood.

there are two meanings 散心 - 1 = be distracted 散心 - 2 = be relaxed

Like Marco said, "to relieve from boredom". It can also mean "to lose concentration". Depends on the context.

When someone is frustrated, he could choose something interesting to do, like traveling, or visiting old friends. 最近他的心情不太好，外出散心了。