I learned the hard way years ago when my Writer's Block opened up. I worked for over two and a half hours writing like there was no tomorrow. At that time I was very new to computers. It never even occurred to me to save periodically. Long story short, the phone rang and I got up to answer it. After chatting with my friend for quite some time I was just crossing the dining room to sit down at my computer again and continue my writing when we got a 'brown out'. It wasn't even a full black out. We did NOT lose power. The lights merely dimmed! But, it was too much for my computer. I LOST everything. This after an EIGHT year block! Needless to say, I cried, swore like a fish wife, and then took a shower. Now, in my game (and when I write) I'm quick to hit the save button. Particularly in my game whenever anything significant occurs.
I feel your pain. Losing a build you've poured your heart and soul into is tormenting. I'm so very sorry that happened to you. Try to shrug it off and rebuild while the memory of it is in your head. And save, save, save every step of the way!