One reason why it is important to be centered in your ego, in your natural self, and in your body when you meditate is so that your needs can be met. So that meditation can be a healing place, that tunes you up for life.
If you are on the path of intimacy (as opposed to being a monk or nun), then sexuality is a major part of your life and your dharma, your way through the world. Even if you are not having sex on a regular basis, welcoming the tingle of electricity through your body is important for your physical and emotional health.
Anger is also important, to notice and care for any feelings of anger anywhere in your body.
Hurt is important, to notice, tend to, soothe, any areas that are feeling hurt.
Exhaustion is important to notice, feel your way into any nerves, muscles, areas of the body that are feeling the strain, feeling tired out, in need of soothing and replenishing.
Boundary invasions, that weird rage feeling when someone crosses your boundaries, invades your space, is an important area of life to attend to, study, learn from, develop responses to.
Basically you want to feel every area of your body and its needs for healing and for expression.
This is where the magic happens.
Let's say you are using breath as your gateway into meditative awareness.
If you can simultaneously delight in the gorgeous generosity of the air, this magic substance that day and night gives us life, while at the same time feeling your desperate need for love, attention, healing, friendship, and safety, then your body will manufacture its own healing chemistry as you breathe.
This is, by the way, what life does. It generates a creative response to every challenge, every need.
Air is magic. This is not scientifically proven yet, but I also think that when we breathe aware of our needs, that we magnetically attract from the prana in air the exact kind of healing magnetism we need. There are some kind of charged particles of life in the air that respond to our need. All the meditation traditions consider this ocean of air we are living in to be generous beyond comprehension.
Most of us are borderline exhausted, like marathon runners, just doing our best ever day to get everything done.
Therefore when you approach meditation, come as your needy, exhausted, joyous, horny, lonely, irritated, angry, hurting self. That way you allow the generosity of life to treat you, heal you, soothe and refresh you.
* Ego is simply the sense of "I." The sense of who you are. What you capabilities and limitations are. What your desires are and the nature of your Path.
** When people try to be perfect in meditation and do not cherish their imperfection, and do not stay in their ego needs, then meditation can be dessicating. They might benefit for 6 months to a year, but then the denial of needs becomes a permanent part of the way energy flows in the body. There are many skilled observers in the world, and among them meditators are famous for becoming robotic and dissociated.