While you have an ego, you will actually defend it and protect it. You will be afraid of the truth because the truth shows that the ego is not real, and if you believe you are the ego, that means you are not real. That would of course be frightening.
It's not so much that our ego resists waking up. It can't wake up. It's just a machine, a structure made of illusions. But WE resist waking up because we're identified with the ego. We interpret the truth through it, ask it what its interpretation of the truth is, and take the truth's "attack" on it personally.
If for example you are identified with the ego and the truth tells you that the world is an illusion, or that your body is an illusion, you - identified with ego - will take that personally. You'll think that it means you are an illusion. Obviously that's confused but you also think it's real, so you'll see the truth as an attack on your very existence.
This is why it can be so difficult to accept the truth and wake up. Our ties to the ego make us believe the illusion is real and that we are the illusion. IF that were true, it's totally understandable that you wouldn't want to let go of your self.
This can be why, when you open up to some truth, letting the light in, you will on the one hand welcome courageously but on the other hand react to it like it's come to destroy you. You will have an ego rebound and feel upset and angry and scared, as though you're being threatened.
Often when I am in a flow or a upswing of inspiration, teaching, writing etc... I am opening up to new truths and expanding my awareness, but at the same time, it is easy to become overwhelmed. I start to have a lot of emotions come up for release. And if I push too hard, I will actually start to feel afraid and guilty. This is the parts of me still attached to the ego which do not understand or accept the truth, and perceive it as meaning all kinds of wrong conclusions. I've found particularly that when I talk about unconscious guilt it can produce a lot of fear because my ego interprets it to mean the guilt is real and therefore I should be afraid.
Exposing yourself to the truth can therefore produce all kinds of reactions, including sickness. Sickness defends against the truth, because you think the truth has come to attack the ego. So basically if you're closely attached to and identified with the ego, the truth will seem very threatening and you will likely produce a lot of sickness in an attempt to protect your sense of "self". It's just self-preservation. The only distortion is that your sense of identity is misplaced so you're taking things personally that do not really apply to who you really are. They apply to the ego, but not you.
Sometimes then I have to take a break from "too much input" and from pushing myself into so much truth at once. But I think over time my rebounds have in general become less intense now. I can talk about the truth for longer before my sense of reality feels the pressure and starts to retaliate. I guess that's good, it means that I am not as ego-identified as I used to be, or that I've woken up some.
Jesus also talks about how when we are at first taking responsibility for everything, we may take it to be a major attack, because to the ego-identified self it implies we must be very guilty. But over time, as we dis-identify with the false self, we don't take it as personally, or to mean that we are guilty as much. Over time it becomes easier to take responsibility knowing that it does not imply you are guilty, as you start to "separate" yourself from the ego's interpretation of it.
Starting to grasp how I have chosen everything I am experiencing, has been blowing my mind and expanding my awareness, but also scaring my ego identification some. Time to relax a bit.