Just say no.
Every single day, you are presented with opportunities. You say "yes" to most of these opportunities not because you want to. You say "yes" because you hate disappointing others, fear missing out and have the tendency to vastly underestimate how much time you really have. You think that saying "yes" to every opportunity that comes your way will get you ahead in life and work but it usually leaves you feeling burnout with little to show for all your fiery effort.
Because you are an ambitious individual, you will never have to worry about undercommitting yourself. You just won't. So, instead, you should practice saying "no". In fact, "no" should become your default answer. If you can't decide on what to do concerning an opportunity, the answer should always be "no". By saying "no", you will disappoint others in the near term but they will respect you more in the long-term. By saying "no", you will notice that most opportunities are actually worth missing out on. By saying "no", you will create more space to do the kind of work that ignites your soul.