Recently I've taken on a role as a production scheduler at my company, so in terms of being a "leader" for one of the management sectors I've taken on planning for some of these projects. I think one of the biggest challenges in planning is having something surprise you. You can be planning for a project and have all your risk assessments done and believe that you should have everything figured out, and then all of a sudden something happens that brings a whole new complexity to the project. For me, that part of planning is difficult but it's also something that I enjoy, as there is always some problem solving to be done in planning. I think also getting the team to also have their input in planning can be a challenge as well. Most people want everything to be laid out for them and all they have to worry about is execution, but I believe a project doesn't become successful without the input of those involved in the execution in the planning process. It's so important to have a good baseline at the planning stage, and without that key information, it can be disastrous for the rest of the project timeline.