Sort:  

Thank you @sidwrites.
On a base level it is survival. Like the time a pack of wolves spotted you and advanced. And you we're quick to climb a nearby tree and be safe. Not you personally, just as an human example. You may have pulled this same save, from this particular memory many times thereafter. Useful indeed, in deed!
On a more advanced level and mostly hidden in our subconscious mind; everything we see, hear, touch, feel, and at other yet unrealized levels, is stored in our mind.
At the close of each day, reflect on the good memories so recall is supported and life becomes more and more positive. I followed you. Also read your formatting post yesterday :-)