Improvement comes from small gains over time. Putting in the work day after day, week after week, and year after year improves performance. The key is consistency.
Spurts of activity (the season) followed by periods of inactivity (summer break, Thanksgiving break, Christmas break, spring break) do not help you improve. This turns into a sinusoidal (wave) of strength and conditioning that doesn't improve over the long term, it simply oscillates throughout the year.
Athleticism can be constantly improved. Their might be highs and lows of intensity and volume to your training, but over the long term you can see linear improvement with consistent attention to strength and conditioning.
Milo of Croton is the oldest example of this type of development that I know. According to myth, he lifted a newborn calf everyday until it grew to full size (then he apparently ate it). Talk about simple training and progressive overload! It seemed to have worked because Milo subsequently won six Olympic medals.
It's not sexy, it doesn't show up on YouTube, and it is hard, put putting in the work day after day, week after week, and year after year improves performance. So, rise and grind.