This is one of the more mystical passages in the Daodejing: the only way to achieve enlightenment is to block your eyes and ears and nose and “use the light” to look inside yourself for wisdom and enlightenment. The more you search outside for knowledge and get caught up in human affairs, the more you risk losing the safety provided by the way.
The universe had a beginning;
It’s called the mother of the universe.
If you find the mother,
You understand her children.
If you understand the children and still cling to their mother;
You will always live free from danger.
Block the holes;
Shut the doors;
And for all your life your strength will not fail you.
Open the holes;
Meddle with affairs;
And for all your life you will be beyond salvation.
Seeing what is small is called enlightenment;
Holding on to weakness is called strength.
Use the light;
Return to enlightenment;
And thus stay clear from danger.
This is called practicing the eternal.