What is meant by the fact that predestination (qadar) does not contradict action, and what is the way to get rid of negative thoughts related to predestination?

The cure for obsessive thoughts is to ignore them, because delving deep into the concept of divine decree (Qadar) opens up a great evil. Allah has concealed the knowledge of Qadar from His creation and has forbidden delving deeply into it. Therefore, a Muslim should supplicate to Allah to rid him of these obsessive thoughts and to keep him steadfast on the truth. He should also have a good opinion of his Lord, for Allah is as His servant expects Him to be. Belief in Qadar does not negate action, for Allah has created causes and effects. The servant must take the necessary means to achieve desired results, while believing that both the cause and the effect are by Allah's decree, and that prior decree does not prevent action but rather necessitates diligence and striving.