Check out some braking tips to improve your ride. Braking is a significant skills that you'll need in order to stop faster, gain seconds when you are running through corners, going down descents and riding in groups.
This video will help you improve your braking skills.
Breaking in corners - breaking puts additional demand on your tires that can potentially overload them that can cause you to lose grip, chances are you can touch the breaks and not lose traction that could've gone through the time faster. The reality is that most of us do breaks in corners but the golden rule is make sure that you let them off when you clear the apex of the corners and then start to accelerate. In emergencies, when you apply the breaks full on mid turn make sure you straigthen up as you turn and then run wide if you can.
Breaking in races - as well as moderating your speed certain braking situations call for slightly different technique and one of this in bunch situations as a bunch turns on a sharp corner is a concertina effect. It means the riders at the back would need to break harder before they reach the corner and ride around slower and then accelerate back at speed afterwards. It's incredibly draining, and can take even a really strong rider apart and something like a criterion race. You can get around this though by doing your break early and leave a small gap between you and the rider in front of you. This little gap will mean that you have to slow down as much on the corner as you can use it to close the gap rolling back onto the wheel on front and exerting more speed.
Air Braking - When you do need to break sit up at the same time your body will act as an air break and improve your stability at the same time.