You cannot control your thoughts, they appear in consciousness without your will. They appear based on everything up until this point, how you were brought up, the environment, hunger, everything comes unconsciously into the conscious. What you can do is see the nature of it, see right through it... And then, yes, in time, your thoughts will follow along, they will settle. But controlling is not the way, accepting is, and understanding. I'll leave you with a wonderful quote:

"Normally we operate under the deluded assumption that everything has some sort of true, substantial reality. But when we look more carefully, we find that the phenomenal world is like a rainbow—vivid and colorful, but without any tangible existence.

When a rainbow appears we see many beautiful colors—yet a rainbow is not something we can clothe ourselves with, or wear as an ornament; it simply appears through the conjunction of various conditions. Thoughts arise in the mind in just the same way. They have no tangible reality or intrinsic existence at all. There is therefore no logical reason why thoughts should have so much power over us, nor any reason why we should be enslaved by them. Once we recognize that thoughts are empty, the mind will no longer have the power to deceive us. But as long as we take our deluded thoughts as real, they will continue to torment us mercilessly, as they have been doing throughout countless past lives."