To be proactive is to deal with small problems before they become big problems. This means you are aware of what can happen if you don't fix it now. This could mean getting anti-virus software so you don't get a virus. Getting a flu shot so you don't get the flu. Or even changing your oil so you don't mess up your car.
active before is the direct translation, means do something before something bad happens. for example, you notice you have a blinker not working on your car, and you change it. had you not done that, someone could've rear-ended you not realizing you were turning.