Describe a situation where your work or an idea was criticized?

Describe a situation where your work or an idea was criticized?
Some years ago I had an idea to create AC rectifier without electrical transformer using only capacitors and relays.My friends criticized that idea.
Some months later I finished construction. The rectifier was able to work, but I wanted to improve it. At that time was lack of high voltage transistors. So my idea remained unfinished.