Working from your to do list! This might surprise you, but it's actually a big time management mistake many people make. Instead of working from your complete to-do list, it's crucial to set a top priority list with a maximum of six to eight items on the list. Set this priority list at the end of each day for the next day. You should work from this priority list, working on item one first until finished then move to item number two. Keep your to do list separate and complete items on this list when you have finished items on your priority list. Also, use your to do list as a way to remember what you MIGHT want to put on your priority list.
Checking emails constantly throughout the day. The biggest problem with this is that it interrupts what you are working on. Every time you are interrupted, you lose momentum and focus. Instead, check your emails in 20-30 minute blocks one to three times per day.

Becoming distracted by elements on your computer, for example email notifications that pop up when you get new emails.

Multi-tasking - doing too many things at one time and half completing all of them. This is much less effective than doing one thing at a time and completing each item before moving to the next. Every time you change to another task you lose momentum and focus. Instead, focus in solid blocks of time from 50 minutes to two hours. Multi-tasking is okay for easy activities such as driving and listening to an educational audio program at the same time, but for anything that requires complex thought, you need to focus on one task at a time. The biggest problem is leaving many tasks incomplete. Multi-tasking is actually okay when you complete each item that you are working on then move to the next, but then that wouldn't really be "multi-tasking" if you complete each task!

Working in an environment where you are prone to being interrupted by other people, phone calls etc. If other people come in and interrupt you constantly, this will be a big time waster. Your train of thought, momentum and flow are interrupted and you won't be able to focus on your priorities.

Starting your day by checking your emails. This can be a huge distraction. Instead, start your day with the top priority on your daily priority list.

Keeping emails in your inbox. If you keep emails in your inbox, you will likely read the same email five times before you action it. Your inbox is not meant to be your to do list. Instead, try to handle all emails when you read them. Either delete it, archive it, delegate it, action it quickly or if you can't finish the task at the time of reading the email, archive your email and put the action on your to do list. Keeping your inbox clear will also help you to keep your mind clearer and more focused.