One challenge in the work environment is that most of the time multiple tasks need to be addressed at the same time. Is that true for you? If it is, does it have to be this way? I don't think so! If you are an exceptional multi-tasker then this might not present a problem for you but if you are more of an effective sequential worker then this is a problem.
In any case, one reason why we have this challenge is that we miss to prioritize our work. Many of us just go ahead and work on whatever task comes our way or whatever task we like to work on. This is not a good use of anyones time. Prioritize the tasks that come up and then work on them in priority order.
It is simple but it is not easy. On a typical day when you attend meetings, check emails you also have to prepare other meetings, get a report out to your team, follow up with other teams to ensure the system or process requirements were correctly understood and many other things. Instead of just reacting to whatever comes your way put some effort into regaining control of your time. Don't jump on every task. Think and prioritize before you start the next task.