expression to every thought

And yet," continued Lord Henry, in his low, musical voice,
and with that graceful wave of the hand that was always so
characteristic of him, and that he had even in his Eton days,
"I believe that if one man were to live out his life fully
and completely, were to give form to every feeling, expression to
every thought, reality to every dream--I believe that the world
would gain such a fresh impulse of joy that we would forget all
the maladies of mediaevalism, and return to the Hellenic ideal--
to something finer, richer than the Hellenic ideal, it may be.
But the bravest man amongst us is afraid of himself.
The mutilation of the savage has its tragic survival in the
self-denial that mars our lives. We are punished for our refusals.
Every impulse that we strive to strangle broods in the mind
and poisons us. The body sins once, and has done with its sin,
for action is a mode of purification. Nothing remains then
but the recollection of a pleasure, or the luxury of a regret.
The only way to get rid of a temptation is to yield to it.
Resist it, and your soul grows sick with longing for the things
it has forbidden to itself, with desire for what its monstrous
laws have made monstrous and unlawful. It has been said
that the great events of the world take place in the brain.
It is in the brain, and the brain only, that the great sins
of the world take place also. You, Mr. Gray, you yourself,
with your rose-red youth and your rose-white boyhood, you have had
passions that have made you afraid, thoughts that have filled you
with terror, day-dreams and sleeping dreams whose mere memory might
stain your cheek with shame--"

Would you explain the bold text?

Thank you