"I have done done some touches to my nonsense fairy language - to its improvement. I often long to work at it and don't let myself 'cause though I love it so it does seem such a mad hobby!"
Tolkien's "mad hobby" was at the very core, the foundation of all his wild success in The Hobbit and The Lord of the Rings. Without the hours spent (stolen from other more "normal" obligations and responsibilities) he might never have written anything at all, at least anything that endures to the present as popular and well-known.
This gives me faint hope, or justification, for the time I spend on seemingly useless endeavors. I enjoy organizing my digital music, cataloging wild plants, hand-coding HTML and CAD...and posting Tolkien quotes!
Will it all pay? How will it benefit me or others?
I don't know.
Sometimes joy is hard to define or categorize.
Sometimes joy sneaks up on a person.
Quotation from The Letters of J. R. R. Tolkien, # 4, page 8.