WHAT is Robert Frost holding on to here?

Perhaps his innermost thoughts, desires, achievements? There's a kind of bravado, in any case, in the face of Time, the changer of everything.

I COULD GIVE ALL TO TIME

To Time it never seems that he is brave

To set himself against the peaks of snow

To lay them level with the running wave,

Nor is he overjoyed when they lie low,

But only grave, contemplative and grave.

What now is inland shall be ocean isle,

Then eddies playing round a sunken reef

Like the curl at the corner of a smile;

And I could share Time's lack of joy or grief

At such a planetary change of style.

I could give all to Time except - except

What I myself have held. But why declare

The things forbidden that while the Customs slept

I have crossed to Safety with? For I am There,

And what I would not part with I have kept.