This is partly the same as the principle of complementary oppostion.
We - and everything else - are part of the All, of everything in existence, which is part of the dao, and the complementary opposite of the Nothing.
I - and every other entity - am an solitary being with a core (identity, ego) and boundaries (in our case: time and space).
You may find that these two states of being are not always in agreement. Your feelings can be very strong, even though you know that in the grand scheme, they do not matter. And so on. This is a conflict between absolute relativeness and relative absoluteness.
This is also a conflict that cannot be resolved. You cannot live outside the All, as you are an integral part of it. You cannot also not lose your identity, as you will not exist without it.
This conflict has driven many people to madness. Others make a choice, usually for themselves. If you want to live in your Dao, you should try to reconcile both states of being in your own live. This is where wu-wei comes in.
Acting as if every action is of the utmost importance, while it does not matter at all.
Speaking as if every word is golden, while they are all worthless.
Being as if your life is the most sacred thing in the world, while your existence is completely irrelevant.
This also adresses a common miscomprehension of wu-wei and modesty. Acting without intention does not mean that you will not act at all. Being completely irrelevant does not mean that you do not matter. Life may be without purpose, but the purpose of your existence lies within your existence itself.
There is no such thing as an enlightend living being. Enlightenment, as defined by being one with Everything, requires you to delete your own identity (ego, or whatever you want to call it), and by doing that, you will no longer exist as the person you are, no longer as an seperate entity. In other words: you will die. Therefore, only dead people can reach enlightenment.
Also, you will reach immortality the moment you die.