Conventional wisdom provides us great principles, say, How to fill a jar with rocks, pebbles and sand, or Time Management Matrix, but often we do not know how to implement these principles. These concepts are great and will remain valid forever, but without a system that implements them, the proverbial rubber never meets the road.
Of course we can also find an endless number of practical tools, such as calendar apps, To-Do List Apps, and daily/monthly/yearly planners that indeed give us practical means for productivity. They are useful but do not solve productivity problem comprehensively. A calendar takes care of your meetings quite well, but what about the rest of your work.
But, to delight of all of us, we have that fool-proof and dream time/work management system, available by name GTD (Getting Things Done). The reason it is fool-proof is that it hits at the root cause of the stress at work. A careful reading of the book by the same name or a guidance by a GTD coach can help you to implement the system. A good implementation of GTD helps to bring back the virtuous cycle of keeping up the promises made and feel good about it and work better to keep up more of them.