I feel I have to contribute a sob story from my younger days, which is peripherally related, but may have some relevance. This was back when applications were largely desktop based.
1.) See gap in market where the existing software is limited in functionality and difficult to use
2.) Develop software where everyone who uses it thinks it's amazing, easy to use, intuitive etc.
3.) Discover that although everyone loves it, it's really hard to market against the entrenched incumbents
4.) We got a salesperson in who after seeing the product agreed to being paid on an if-and-when the product succeeds basis
5.) Started looking for synergies and partnerships to help market it. Our salesperson had a lot of industry contacts and he used them to find out who the best people were to talk to at various organisations. He also managed to get introductions to some people. Other companies he found out who to approach just by doing some basic research, calling the company and asking around etc.
6.) Found an appropriate partner with huge customer base who was interested in providing it to their users
7.) They show interest, get NDA, legal agreement etc. drawn up, start negotiating
8.) Spend months demoing product, negotiating, graduating into meetings with increasingly senior staff etc.
9.) The main person we were dealing with is replaced with someone else, things go very quiet for a while
10.) After much deliberating be told that they've decided that the product wouldn't provide sufficient benefit for their users so they've decided not to go ahead
11.) Watch them launch a grossly inferior clone of your product a year later and win sweeping accolades
12.) Lawyer tells you initial legal agreement isn't worth paper it's written on
Then we considered open sourcing the product, but it turned out to be a nightmare because we'd used so many 3rd party components that it would've require huge amounts of work to get to a point where we could do so and we'd poured too much time and effort into it already.
As you can see, plenty of mistakes were made. I learnt a lot in the process though. I don't regret a moment of it.