Just to take a different approach to the more philosophical responses, make sure everything is well with the more concrete aspects of your life. We are made to care, we are made to be motivated and content; I truly believe that when we are not, it's because something else is preventing your body and your mind from working as they are supposed to work. Are you working too much and over-stressed? Are you sleeping and eating well? Do you make time to let your mind just wander? From personal experience, I cannot stress enough how important these things are, especially having enough sleep. If all of these are in order, you'll get an idea for a project, or you'll meet someone, or you'll just enjoy one particular moment, and it will have meaning to you. You'll be motivated and encouraged, it will matter. I don't spend much time searching for meaning anymore, I try to work to remove the things that are blocking it.