there is a sense of erraticism between any kind of interpersonal relationship we are in. its a kind of unpredictability - a potential to discourse or to break. it may not necessarily be a darkness, but it refrains one from uncovering it.
it is at the back of our head. subconsciously, we are drawn by it and it leads us to commit certain incomprehensible acts to the ones we are having the relationship with. it blocks out your judgment and you seem to only act as how you will react.
but when you take a step back and give it a second of thought, you will start to realize the rooted cause of this erraticism. you will begin to understand the levels of your relationship with that someone and see how complex they may be - your feelings, his feelings, your desires, her desires, your state of mind, their states of mind.
and when you realize it all, it may just dawn on you how much you should be valuing your relationship with that person. Never to take them for granted and to accept them for who they are. after all, it is because of them that you seem to act in this impulsive manner.