Stuart's and Tommy's answers are both good. Just to add to these answers, I'll mention that you can also talk about "getting yourself under control." Like Tommy's example ("Mr. Smith is under control"), this means that YOU are the problem, and you have to control yourself.
If someone is acting crazy, you can say that the person "needs to get himself under control." In this case, the person is the situation that needs to be controlled -- but he is also the person who needs to perform the act of controlling. If he succeeds, then he will be "in control" and will also "have himself under control," because he will be controlling himself.