How does Robert Browning try to convince the reader that an attempt is more important than the ultimate achievement of experience in life in the poem "The Last Ride Together"?

The speaker of the poem mourns the end of a relationship, and he asks at the end of the first stanza for "one more last ride" with the "mistress." It is the mistress he is addressing; she is, apparently, breaking it off with him.
He hopes for a final chance to feel "deified" just by sitting with her and being in her presence a bit longer. (It is also possible that he longs not just for one last "ride" with her but for one more sexual encounter.) He considers his past hopes and how she might never have loved him at all had he never tried to woo her; she might even have hated him!
He asks, "Where had I been now if the worst befell?" He wonders where he would be now if the worst had happened. It seems better, then, that he tried to win her, because at least he got to be with her for a little while. He did not fail in either word or deed, and there was some success to be had in the striving.