Imagine an elite squadron of thunderous charging cavalry. At their helm is the commander who is faced with a decision. He can thin out his men and charge the entire enemy line. Or he can wedge his ranks, focus on one strategic weak point, and thunderously hammer the enemy with might and precision! The latter is clearly more advantageous.
Sometimes it is useless to attempt many activities at once. It is not a question of “will I have time to complete all this?” but rather “how can I produce great quality work?” If quality is what you strive for, then it is necessary to recalibrate your focus towards a smaller number of important activities.
The amount of time you spend on something isn’t the most important factor. You can spend countless hours struggling on many things and develop mediocrity in a few. Or you can focus on a single task and develop mastery. Great ideas are derived from focusing on a few big ideas, and deductively building upon them to generate deeper understanding through connections. Great ideas come from a focused mind. A focused mind comes from doing less.