1 - Delegate and Outsource. One of the biggest things that you can do to improve your time management is actually simple to understand. You do not need to do everything, let alone do it all in one day. Rather than try to take everything on by yourself, learn how to delegate and outsource by offering parts of projects to those who can help. If you believe that someone can manage part of a project more efficiently than you, ask for their help. Focus on the parts of projects that you know that you can complete, and do not allow yourself to become overwhelmed by the details.
2 - Set Time Limits and Time Budgets. Every task that you tackle should have a realistic time limit or time budget set for it. This way, you can better work productively on each and every task based on individual time limits. When you give a task an indefinite amount of time, or when you try to tack a single time limit onto a very large project, it is much more difficult to get things done in a timely manner. Instead, allow each facet of a project to have a time budget and you will be able to get a lot more accomplished.
3 - Learn to Say No. You need to learn how to say no not only to your own self, but also to other people in your life who have unrealistic expectations of you. People often take on far too much and that is one of the largest causes of things simply not getting accomplished. Don't take on more than you can handle, letting yourself and other people down in the process. Instead, simply learn how to say no when you do not think that you can accomplish a given task, rather than taking it on and allowing for it to overwhelm you further.