Well your thoughts dilute over time as well as your recollection of those thoughts. Your valuable mental clarity deteriorates and prevents you from reacting appropriately to situations.
Mind and brain researchers studying thought discovered that 84-92% of the thoughts you think today where the same thoughts you thought yesterday.
Your accumulated emotional hurts, wounds and triggers have a way of making you feel obsessed with recalling your past thoughts in an attempt know what you really thought at the time, what did happen for sure or thinking your latent thoughts are a template of what to do or not do in the future. Unfortunately gaining clear and accurate recall of your latent thoughts from your past is nearly impossible and extremely frustrating. No one else who was with you during those times, recall your thoughts the same as you do now.
But what happens is you become immersed into what is termed black thinking or delusional thinking. Black thinking is the obsessive thinking over latent thoughts from times gone by. In fact black thinking are thoughts that have been diluted or become unrealistic due to time passing and repetitive recall. Simply all thought dilutes over time.
Thoughts become distorted, unrealistic, out of context or slanted away from the original true form. Funny though that black thinking seems to now fit your perceptual recall needs about certain situations. This type of thinking can get stuck in your mind and make you obsessively think over the thoughts again and again gaining no closure or resolution. Black thinking can be seductive as well as very destructive in the moment.
The content of these dark thoughts you obsess on originate from false beliefs, old dilutes ideas, doubts, and self-judgments that form from your experiences as well as sabotaging and critical thinking. When you become engrossed in right and wrong with yourself over thoughts, true or not, you tend to take it personally and you treat every statement in your head as a personal affront. Taking your own thoughts personally causes you to be very disappointed in yourself. Therefore you mentally get pulled down into deep black waters in your mind.