What are main reasons for slow development of a project?

If a project implementation is not moving as it is expected, or you are not meeting the expected date of completion, you could look into your plan see what were the foreseable barriers you have identified during the planning stage of the project. Usually, this question can be answered as well as identified if it had been forecasted during the planning stage. If not, then it is time to sit down again, identify the factors that contribute to slowing down of the project's development and address it. It may also be helpful to look unto the plan again and try to forecast the problems that may arise during each stage f the project implementation process. When this is accomplished, then it will also be helpful that a solution be formulated for every possible problems the project may face during its actual implementation.