"If you fail to plan, you are planning to fail!" -Benjamin Franklin
One of the biggest pitfalls that we're all prone to fall into if we're not careful is rationalizing with ourselves that things on our to do list don't actually need to be done. For example, it can be tempting to think, "Why do I need to write down a to do list or a shopping list? I'll just remember it in my head!" However, there is quite a bit of empirical evidence indicating that people are substantially more likely to follow through on a task if they write it down.
In "The Paradox of Choice" by Barry Schwarz, he describes how it is more difficult for people to make sound decision when they are bombarded with a plethora of conflicting options. But most importantly, he claims that having too many choices leaves people unhappy. This same concept applies to your task list: the more tasks you have, the more difficult it is to accomplish them.
Human beings are hardwired to like to complete tasks, close the loop, hear the end of the story, etc. It is imperative that your task list makes you feel accomplished, NOT paralyzed. This is why I never make it a goal to accomplish more than 5 tasks maximum: I don't want to set myself to fail.