Unless you're a professional driver, getting behind the wheel of a car without brakes is extremely dangerous. While you may not plan on driving in such conditions, if your brakes are in poor health you could find that when you try to bring your car to a stop, you'll have some trouble. Typically, brakes do not just give out entirely without warning, and these red flags should be addressed as soon as they are noticed to avoid further damage.
If you've noticed your brake pedal feel soft or spongy, possibly without enabling the brakes as soon as you apply pressure, this may indicate a few different problems. The most common cause of soft brakes is air in the lines. With the engine running and the car in park, try pressing the brake pedal a few times. It should gradually lose that spongy feeling as it is used more. While this temporarily fixes the issue, leaving the brakes alone for a period of time will bring things right back to the way they were.
Air can find its way into the system through a number of routes. When there is not enough brake fluid in the lines, the leftover space will be filled with air. A leak in the system can not only lead to fluid loss, but this same hole can allow air to enter the brakes. Air can also find its way in when you service or replace a part like a caliper.
The only way to remove air from the brake system is by bleeding the brakes. However, if done incorrectly, air will still be present and you'll need to repeat the process. Bleeding should be done every few years anyway, to remove old, used fluid and replace it with new. Most cars' brake systems include a bleeder valve for this purpose. Depending on the make and model of your vehicle, the wheel may need to be removed to access this part.
You will need someone to help you with this project, a couple of fresh cans of brake fluid, a turkey baster, some plastic tubing, a container to collect the old fluid, rags and rubber gloves. Start by ensuring the bleeder valves can be loosened, but do not unscrew them just yet.
Next, open up the brake fluid reservoir and use the baster to suck out all the liquid and as much sediment (if any) from the container. Be sure to wear gloves and other protective gear, as this fluid is corrosive. Clean it with a rag to remove any leftover particles, and then move on to the bleeder valves.
Grab the rubber tubing and push one end over the valve, placing the other end in the container, and add an inch or two of clean fluid to prevent air from finding its way into the system when you open it up. Then, top off the reservoir with new brake fluid and replace the cover.
Have your assistant apply a small amount of pressure to the brake pedal as if they were slowing the vehicle, but not trying to stop it completely. They will need to keep constant pressure as you loosen the valve about a quarter turn. When you do this, a small amount of old, dirty fluid should pour out of the car and into the container. As soon as it stops, have your assistant release the brake. Continue doing this until the fluid runs clear, and add more fluid every few cycles. Repeat the process for each brake, making sure air cannot enter the bleeder valve from the other end of the tubing or even the space around the tube and the valve.