For the longest time, as in until the first draft of my first book was written, only my husband knew about the double life I lived--soccer mom by day, aspiring author by night. The only reason I told him, was because I had to explain why he would be watching TV by himself at night for the next several months.
When I told him I was going to write a book, I was actually giggly with embarrassment. I half expected him to laugh at me, but he didn't. I'm not going to get all sappy and say my husband was my number one supporter, because . . . well . . . he wasn't (men can be big babies at times--especially when they feel like they're being neglected). However, he never faltered in his belief in me. He never doubted my ability to write a novel and to some day get it published (still working on that part). I once asked him why he never doubted I would finish it, and he said "Because this is you we're talking about."
Despite his confidence in me (two years ago), I still felt it necessary to come up with a back-up plan. I gave myself a year to try this writing thing out. I would write my book, attempt to get it represented, and then if nothing panned out, I would happily (slight exaggeration) join the part-time workforce. Needless to say, that year came and went. As soon as the school-year started, I half expected my husband to start leaving the help-wanted section next to the coffee-maker every morning, but he didn't. When I approached him about holding off finding a job so I could work on my writing, he said, "Okay," followed by, "Yeah, I don't think you should give up on this." That was a year ago, and the conversation of me going back to work has never been brought up since. He could've been a jerk about the whole thing and insisted I get a job and stop typing away on the computer all day, but he didn't.
I am so proud of my husband. He works long, hard hours doing a manual-labor job. He deals with crappy coworkers and working conditions. He goes to work with sore muscles and pinched nerves sometimes. This is part of the reason I keep going. He works his butt off to provide for his family, and so that I can chase my dream. He believes I can succeed, and I don't want to let him down.
Whether or not spouses/significant others understand or are interested in what we're doing doesn't really matter, but their belief in us does.