Here's how you can recover from a failed game design concept.

The post-mortem document allows you to review all development phases, not just the concept, by analyzing decisions and their impacts, whether positive or negative. It can cover various aspects, from game mechanics and technical limitations to received feedback and design choices, along with their reasoning. Creating this document provides insights into what you could change in future projects and helps you reflect on the lessons learned from this experience.

More often than not, assessing process is the key to assessing failure. Because ultimately failure is inevitable on all projects, the successful ones just learned how to fail faster and iterate faster on those failures. Also, keep in mind that sometimes there is nothing you or the team could have done. Unfortunately there is also a large amount of luck involved in any successful project.

Reach out to people in person, and let them playtest your game. Observe and analyze their reactions and ask for their feedback. Their reaction will help you understand how good your game's user experience is. Do they interpret your game as you expected ? You can identify potential issues, understand player interpretation and gather insights to improve your game design concepts.

Keep in mind that feedback should be sought throughout the entire development process. Schedule playtests with friends whenever you have a new prototype or version ready. This helps you test if the game is fun and observe how people react to your project or improvements. During playtests, avoid interrupting. Focus on noting players' reactions to different events and actions. If possible, ask them to think aloud during the process to better understand their thoughts. This approach helps you avoid major failures after long development periods. If something goes wrong, you'll know much sooner and can rethink your concept accordingly.

This should be something that is done at EVERY stage of production, not just after failures. Feedback isn't just invaluable, it's necessary for every project!

While it is important to get back on the horse, it's also important to grieve a little bit. Yes, grieve. A lot of dedication goes into every project, and there can be a depression that sets in after a failure. It's ok to take some time away if you can, do something else entirely and then come back fresh. Once you feel far enough away from the effects of the failed project, you'll find diving in is much easier now.

Go and watch GMTK on youtube no seriously when it comes to game design and mechanics GMTK is one of the best (if not the best) resource available on the topic.