Prioritization and knowing your work limits are the keys to getting things done. If something is not a priority it is deferred until it becomes one (after current priorities are completed). And when setting priorities, there is a cutoff. Sometimes you can work on more than one priority. Do it. But if only one can be worked on without issue then one it is. I have always known my limits and never take on more than I can handle. If I do, it causes problems for myself and others. Everyone has limits. Doing a little on each of a lot is not productive.