One of my greatest project management failures occurred early in my career when I underappreciated the importance of stakeholder alignment. I managed a project where key decisions were delayed because I didn't involve all relevant stakeholders from the beginning. This caused confusion, scope changes, and ultimately delayed delivery.
From it, I was able to gather that stakeholder communication is paramount. I involved all the people in the plans from the starting point. First, I do clear documentation with regular updates. I also focus on active feedback loops so that no mistake is made without proper coordination between the stakeholders, which leads the project astray.