The funnel effect is a really good analogy of why you should limit your work in progress, like I do on my Personal Kanban. In the analogy, just the right amount of water can go through as fast as it's put into the funnel. But add extra water to the funnel, and the whole thing backs up.
In reality, keeping focus on just the right amount of work can allow you to finish more than if you didn't. Personally, I limit my work in progress to 3 items. I never thought it would have such a positive impact. So, what do you have to lose? Do you have a long list of to-do's, doing a little here and doing a little there? Do you ever feel like you're not actually getting anything done? Today, rather than trying to multitask, focus on just a few tasks until they are DONE. If you complete one task, you can add another to your focus list. Remember, 99% done is still not done. At the end of the day, you'll feel a sense of accomplishment, preventing a traffic jam of work and actually getting stuff done.