You would trade most of what you own for one true thing to stand on. Every answer so far has dimmed once you got close to it.
What it looks like in a life
Everyone born in those years has the sign, so the house is what makes the search yours. In the 9th it is faith, foreign places, and teachers: you go, you believe, you come home different, and eventually the teaching thins out. In the 3rd it is a daily mind that runs on hope and gets loose with the facts. In the 10th it is a career people read as a calling before you have worked out what it is. Aspects tell you the pattern. Neptune on Jupiter makes the belief expand faster than the evidence. Neptune on the Sun means your identity keeps getting rebuilt around whatever you last believed.
The gift
Real faith comes easy to you, and it spreads. People borrow hope from you without noticing they did it. You can hold a big picture without needing the proof in hand first, which is what lets you start something that has no track record yet. When your belief is aimed at something true, you are convincing in a way that no argument can match.
The friction
You outsource the search. The teacher, the doctrine, the destination, the next country: each one carries the answer for a while and then goes grey. Searching becomes the thing you do instead of arriving. You believe first and examine later, so you have signed on to more than one thing you would not sign now.
The esoteric layer
Neptune was discovered in 1846, so the old traditions never accounted for it. This layer is modern and Bailey's. Bailey calls Neptune sacred and puts it on the sixth ray, devotion, and Sagittarius carries that same sixth ray, so devotion doubles in this placement. He also gives the sign a second ruler for the awakened person: the Earth itself. That is the correction. The goal is not up there or over there, and the keynote says it plainly: "I see the goal. I reach the goal, and then I see another." Ride it into the ground of an actual life.
Where this goes
The house says where you keep going looking, and the aspects say what keeps dissolving on you once you arrive. A full natal reading names the thing you were actually after, and it is more specific than any doctrine.
Related
See it in your own chart
Cast your chart free and read this placement next to everything else you carry.