When in the long-drawn avenues of Thought

When in the long-drawn avenues of Thought
I halt, and look before me and behind,
And seek what erst I all too little sought,
Some spot secure of rest, I do not find.
Retrace my steps I dare not, lest each nook
I late rejected should reject me now,
And sweetest arbours, restlessly forsook,
No more be prone their leafage to allow.
So to the untrod distance do I strain,
Which seemeth ever further to extend;
Desiring oft, in irritable pain,
Premature sleep would bring that settled End,
When I shall know it all, or else forget
This far too little which for more doth fret.