Not everyone is good with time management. People have trouble budgeting their time appropriately and they don't get things done like they should. This is often a problem with studying and completing work for students and also for those who work in the business world.
One of the best ways to improve your time management is to block out certain areas of time. How much time can you sit and study something before you become restless? An hour? Thirty minutes? It's important to find that out, so that you can schedule your study time with breaks. If you study for half an hour and then take a fifteen minute break and then study again, you will likely get a lot more done and retain more than if you take no break. You'll be restless and you won't remember what you study if you don't give your mind rest breaks from time to time.
You can also find a lot of other small times to study, like when you're riding the bus or waiting for a friend to arrive. Don't waste that time. Use it wisely.