Ego
Your ego is your sense of self separate from everyone and everything else.
Its sole purpose is self-preservation. It protects you from harm from others, and from self. It uses basic instinct characteristics to keep you away from things that it thinks might harm you, and draw you closer to things that will protect you. It uses fear, anxiety, “should”, need, want, desire, etc. to drive you to or away from what it thinks will give you the best chance of survival. There is one problem though, the ego does not know the big picture. It forgot why you are here, and it is not merely to survive. Its purpose is not in line with our greater purpose; however, without it, we might not be alive long enough to fulfill our purpose, so it has to exist. The key is knowing when to listen to it, when to let it go, and when to seek higher guidance.
Your ego is not bad or good, right or wrong, evil or benevolent. It just is. It is you. Just like your higher self is you. It is using your past experiences from this lifetime fairly consciously and from your past lifetimes fairly unconsciously to steer toward the safest path. This can be a very good thing. It can also be a very treacherous thing and counterproductive to your higher purpose. Your ego has forgotten why you are here and only thinks of its purpose which is to protect you, but your protection is not your purpose. It is possibly necessary for you to fulfill your purpose to have that protection, but if it stops you from seeking what you need to fulfill it, then it does not serve you or your higher self anymore.