If you're an online seller, you mentally have certain expectations and hopes about your product. I always thought "Maybe this is the next pet rock or Cabbage Patch doll or hula hoop"......wrong approach.
False or misleading expectations can lead to disappointments. Beauty is in the eye....you know the phrase! And what I may think is an indispensable thing of beauty and function can be seen as a worthless piece of junk by another.
Make what you like. Create what you believe in. Find a niche. Prepare to be disappointed and then it won't hurt as much. We have winners and bombs and with that comes experience and knowledge. Don't over inflate your expectations. If one or two sell, terrific. Three, very nice. Four,hmmmm, maybe you have something. Take it slow. Do your research. Listen to experienced friends. Don't overstock with supplies, just in case.
The world changes so fast it is hard to keep up. One of my "winners" are my magnetic bookmarks. I have been very pleased with the sales. I had a reasonable expectation but I did NOT anticipate (how could I?) the advent of the Kindle and the Nook tablet readers? Many still read 'real' books but now I have to pause and adjust the expectation.
Again, create what you enjoy and love to do. There are bound to be others with your sensibilities and they will enjoy your product. Just don't expect there to be a line outside your door with crowd control guards...not likely.