@MercurialBuilding The ego acts as a filter between the world and your conscious mind, and your subconscious and conscious mind. It's basically like a lens through which you view things. Its constructive in the sense that you build it with ideas (generally subconsciously), although it can be disassembled as well, i.e. it contains things like your identity and values and overall fixed idea of your worldview. For most people it acts as a sort of series of defense mechanisms to keep troublesome issues out of their active awareness. For example if you have a shitty boss you might deploy the ego while you're in the office to suppress your resent at him, and then let your resent out after work. (This is a benign example of the ego being fluidly deployed to get through the day.) An unhealthy example would be something like suppressing an insecurity which ends up later controlling your behaviour without you being actively aware of it. Or only being able to relate to someone in conversation by comparing their experiences to yours.

People with large egos are generally self centred because they have an overly particular lens through which they judge and experience the world. People with small egos are generally more fluid and empathetic because they can judge and experience the world with less prejudice.