Trying to find causes of everything

Is trying to find causes of everything not a good practise? Isn't having rational mind a good thing? I know that the Lord Buddha advised us to not to think about beginning of life. Because it make us crazy. There may be some other things like this. I realize that this thinking causes me to loose sati. Why that thing happen? How long does it exists? etc. Most of these thinking causes to stuck at a loop. It feels like it wastes lot of energy for nonsense. But I have fear of stopping this. Do I have to just stop thinking and let it go? Do I have to forget things without knowing causes of it? How do I select what to think and what not to think? How this affects sati? What Lord Buddha said about this? How should I handle this rationality?