how do i prevent thoughts from taking over my mind throughout the day?
Meditation and being mindful of every time your mind wanders off, to try and catch it and revert yourself, reverting your mind back to the present moment.
I found that staying busy really helps take my mind of things, especially unwanted thoughts.
Meditation and mindfulness hasn't always worked for me, in these cases I tend to try to stay as busy as I can, just to not think about things.
I don't know how healthy this is, or if it's a good approach, but sometimes it's the only thing that helps.