Everything you struggle with is at the root of an emotional struggle. Even though some problems seem to be mental, they still have their roots in the emotional body. For example: overthinking seems to be a mental problem that actually stems from a feeling of insecurity or fear of the future. Another example is the fear of heights. It’s not the actual height you fear it’s the emotional issue of fearing the fall or fearing the loss of control. Because all of these struggles are so deeply rooted, you will never really succeed when you try to let go of something just on the mental level. 

Thoughts are messengers. They are messengers of your emotions. Thoughts reflect your current vibrational state of being which is caused by your emotions. So any thought you think is pointing you towards an emotion you feel. So any reoccurring thought you have is constantly pointing you towards an emotion you repress. 
This technique is applied in the form of guided meditations.