I have a friend who's a professional painter and she says that to make it as an artist, producing art is only like 20% of the process. The rest is networking, marketing, and accounting. She's basically a small business. She says most of her time is spent advertising her art, joining artist communities, and re-calculating her budget every month. She went through years of trial and error to succeed, and she did this because she listened to criticism and constantly improved.

It's the same with every creative project. It's not enough for you to have a stack of patents -- you need to learn about copyright law, marketing, and manufacturing. The optimism/pessimism oversimplification is a false dichotomy -- you absolutely need to listen to the naysayers because they'll tell you the weak points in your inventions. Your friend telling you why your ideas won't work will help you optimize your designs and create several backup plans. Don't discount his opinions.