The point of knowing mathematics is to get the answer to problems right? Preferably the correct answer. Otherwise what's the point?
Mathematics isn't just an end in itself. It isn't something to learn so you know math. At its most useful mathematics is a tool that lets us do other things. It's a tool that gives us insight into the world around us. Learning to use math as a tool not only makes it more practical but much more useful.
Which is why Sanjoy Mahajan's book Street-Fighting Mathematics: The Art of Educated Guessing and Opportunistic Problem Solving (Creative Commons pdf) is such a great read. Working through various approaches to help make informed guesstimates and improve your mathematical problem solving skills he makes practical math skills much less intimidating. If you want a very practical book to help you improve how you use math, instead of just how to improve you math skills, then I suggest Street-Fighting Mathematics.