I'm in the early stages of my writing career where the measure of "success" can be marked with easily notable milestones. The big ones along the path still stand out. Actually finished a novel! Full request on my query letter! Offer of representation! Really nice rejection letter!
And, of course, those stood out because those were the things I could grasp on to in the moment. They were little things that represent huge victories.
But they were also victories that were challenging to really talk about or celebrate, as they lacked tangible benefits. When I talked about this to an actor friend, he likened it to getting a third callback on a major movie role. Yeah, it shows you're getting there, that people notice your work... but it's not really anything beyond the humblebrag.
I think those are vital toeholds as you work your way up the wall. You need those little things. You need those few encouraging words you might get along the way.
Even now, with the initial trappings of "making it"-- I've got the contract, the publishing deal, the gorgeous cover, the release date-- it's hard to call myself a "success". The book hasn't come out yet, no reviews, that lingering voice of doubt whispering in my ear that no one is really going to like it.
I don't let myself listen to that voice.
"Success" is always over the next horizon. I mean that in the best way-- I don't think it's some ephemeral thing that can never be reached. I mean that the act itself of progressing toward it is, in and of itself, the real success. It's reaching a new plateau, taking a brief moment to savor that, and then looking up at the next one and saying, "Yeah, that's where I'm going to go."
All right, off to the word mines. See you in there.