I learned to fly at Santa Monica Airport (KSMO), which has one runway, 3-21. So, as a budding pilot, any time I would go to an airport with multiple runways such as Van Nuys (KVNY), which has two parallel runways or Long Beach (KLGB), which has five intersecting runways, there were some extra thinking and planning required prior to taking off.
If you’re flying into an airport with parallel runways it’s clearly important to stay out of the flight path of the other runway or runways. Therefore, you need to be extra aware of your position in the pattern. You may want to cut the base leg a bit short to avoid overshooting the final leg and intersecting the approach path for a parallel runway. There is simply very little room for error and it’s better to stay on the safe side.