come to one's own

I exist as I am, that is enough. --> I am self content/self satisfied.

If no other in the world be aware I sit content. --> I am self content/self satisfied; what others think matters not, even if no one is aware.

And if each and all be aware I sit content. --> I am self content/self satisfied; what other think matters not, even if everyone is aware.

One world is aware and by far the largest to me, and that is myself. --> All that matters is that I am content/satisfied with myself.

And whether I come to my own to-day or in ten thousand or ten million years, I can cheerfully take it now, or with equal cheerfulness I can wait. -- I come to my own one day means to die. I am so content/satisfied with myself that I would cheerfully die now or cheerfully die later. It doesn't matter. All that matters is that I am content/satisfied with myself.

To come to my own to-day has nothing to do with to come into one's own. The author has made it abundantly clear he's already done that. In context, to come to my own to-day means to come to my own end to-day, to die today.

In that poem it is preceded by the lines

If no other in the world be aware I sit content,

And if each and all be aware I sit content.

One world is aware and by far the largest to me, and that is myself,

He is dismissing recognition as unimportant. It seems plausible that by "come to my own" he means "come into my own" - to be recognized as successful.

(Then again, I am almost certain I've read "come to my own" in other contexts to mean death and it fits the poem too, but I can't seem to find anything like that...)

edit: Thinking it over, I'm certain that the meaning here is recognition, not death. This piece is as far from nihilistic as it gets and saying I can cheerfully die now or in a million years doesn't quite fit. (That, and he calls himself "deathless")

edit 2: On third thought. Poetry...

I should delete my answer but I'll leave it just for the record. Death seems to be a possible (probable?) meaning: "I am deathless [...] I shall not pass [...] my foothold is tenon'd and mortis'd in granite (strong) I laugh at what you call dissolution." See @RichardKayer answer.