Nothing is real unless it exists in the outside world.
Your thoughts are not real. You cannot control them. But you can control the environment that affects them.
You cannot control where a dog urinates during a friendly neighbourhood walk. Will it be on the stump of a tree today? Or will it very coincidentally be under the letterbox of the old man across the street you do not particularly like? You cannot precisely determine this, even knowing it would almost certainly occur at some point during the stroll, but you can create lessons and precedents to influence what is considered more acceptable and what is considered less so.
Your thoughts are a wild farm animal zipping around in a fenced paddock. In a particular instance, the beast runs where it wants. At any given moment, you cannot decide exactly where in that enclosed field the your thoughts are. This level of microscopic precision is out of your control.
However, by maintaining an environment conducive to the kind of thoughts that you would like, you can control the dimensions, the weather and the general disposition of that paddock.
It is okay to be human.
Humans cannot control their exact thoughts but, over time, they are very good at meddling with man-made objects and putting artificial restrictions on things.
This is positive psychology 101: you can influence the world around you in order to become less of a grump.