One thing that you don't want to happen is your brakes going out from a failure; these are generally associated with your brake master cylinder failing. There are a few things you can look for to determine if this is the case, and make repairs before a serious accident can occur.
1. Loss of Brakes Pressure
If you can apply pressure to the brakes and the pedal goes to the floor without much resistance, it can be a number of things causing this problem. This could be air in the lines, a cap that was not replaced when refilling your brake fluid or a failure in your brake master cylinder. Rule out the other two issues by bleeding your brakes and making sure that the cap on the fluid well is closed and sealed tightly.
2. Brake Pedal goes to the Floor
Another thing that could be causing a loss in pressure is if lines are ballooning as pressure is applied; this has been known to happen and go unnoticed. What happens is the pressure to seize the brakes is instead squishing into a weak spot in the hose and blowing up like a balloon causing the brakes not to function properly. It could also be broken lines that are leaking fluid from the system, which causes the brake master cylinder not to function properly.