If I can give you one bit of advice for you to be successful in life it is this. Learn to prioritize. Burn this statement in you head. Think about it every time you have to decide what to do next. Prioritization. it is just one simple word and yet so few people or organizations do it well.
I have seen so many projects, products, and companies fail for the simple inability to know what is truly important and make sure that it gets done and it gets done well. Most people tackle hard problems with a shotgun approach. It is the simplest way to try to solve a problem but it is always the wrong way. Rather than take the time to do some thinking upfront or to take a risk that the wrong thing will get done, organizations try to "minimize" their risk by dividing their resources and tackling the problem from several different angles. Of course, very few organizations have the resources to be able to do multiple things well. So rather than do one thing really well, they do ten things really poorly.
The reason most people can't prioritize is because humans hate to be the bad guy. Setting priorities means telling someone "no" or that what they want is going to have to wait. Everyone thinks their problem is the most important. Of course, there can only be one problem that is really the most important so the vast majority of people are going to be disappointed.
Further, it also means knowing who you are. This implies knowing who you are not. Believe it or not, most companies are unable to answer this question. Companies want to be everything to all people. However, taking this approach means you are nothing to no one. If you know who you are this makes knowing what you should do pretty easy and the priorities just line up.
So if you find yourself with too much to do and yet you are not accomplishing very much, prioritize your work. Give everything a numbered priority. There are no ties. Understand what is important and then start from the top.