I've learned that lesson and I guess am learning it incrementally. For years I have flipped anything I can put a tag on and it seems that the hardest ones to sell are the ones that are the 'nicest'(most expensive). The fine line is selling the as-is or making it a little better. Since my current income job is working in a recondition/service facility for fitnesss equipment and it has been educational in what the fine line between as is and good enough can be, rather than making sweet perfection.
There is also a distinction between the hobby side and making a profit. In my landscape/mowing hobby I make a profit since the work using the restored tractors(a pricey hobby too) yeilds almost $25-30 per hour of labor worked. Bikes on the other hand barely yield anything per hour but they can be done in the living room while watching tv, compared to sweating and being dirty. For that reason I call bikes a hobby that can recover costs, not a profit.