If you are an "experienced" project manager and haven't had a few project failures, in my mind, you aren't a very good project manager. Project managers must constantly push their team members towards exceeding their comfort levels, take (calculated) risks, be decisive, make firm commitments, and be aggressive when base-lining and managing the triple constraints (Time, Cost, Quality). Just like a successful NASCAR driver, a project manager must learn to live close to the edge of disaster, but while doing so, he or she must aggressively manage their project’s Risks.
In my opinion, too many project managers are unwilling to set firm expectations with their team for fear of being unpopular. There are going to be times when your project team doesn't really care if a milestone is missed or a promise isn't kept. The problem is your project isn't always your team’s top concern. Don’t forget that. You live with and for your project and at the same time some of your team members might loathe your project. Many team members have other responsibilities outside of your project and your project may be preventing them from doing their regular job.
Project Tip - If you find that you have members on your project team that aren't 100% committed to achieving the goals of your project, you need to start thinking about replacing them.
Based upon my experience, - at least on IT projects - most project problems that are encountered in the Project Execution phases are the fault of the project manager. Proper Risk Management will help the project manager foresee and mitigate many problems that will arise during project execution. If you have lots of problems and issues on your project you did a poor job of Risk Management in the planning phase.
Some things to keep in mind to avoid failure when planning your project:
Be crystal clear when communicating with your team. All important communications should be in writing.
Don't allow project committees or executive oversight groups to dictate how you plan your project.
Communicate quickly to your team and senior management if you believe that your project is out of control.
Don't assume that suppliers or vendors will be honest with you. Make sure you continually follow-up and get commitments in writing (preferably in the contract).
Split your project into manageable phases.
Ensure that your end users are involved every step of the way.
Communicate Status as often as is needed. Include bad news, problems, issues, and concerns in your status report and be sure to include how you plan to overcome them.
Don't let your project fail because you aren't communicating or your team isn't functioning properly.
Believe in the statement that “Project failure is always the Project Manager's fault”!