There are more ideas in the world than lifetimes to do them in - so picking the right ones to pursue is a tricky process.
Whether it is a career decision to specialise in this niche or that.
A decision to follow one project or another.
What to devote your time to in a day, week or month.
Or simply what to glean and take from a book.
Every choice to take on something is to disqualify other options. You choose what to be or do by choosing what NOT to.
It is a flip from the usual way of defining yourself as what you are, and because of that, one that gets you to ask the better questions...
The finer grained the choice, the less differences between them, the more important it is to know what NOT to do rather than what to do. It is easy to commit to a life of a gymnast rather than a mathematician if you are athletic and hate arithmatic. It is far more difficult to choose between one career specialisation and another however.
Making these niche choices is not just more difficult but a much higher value than general ones. When you decide to put a flag in the ground and make a binary distinction betwen here and 2cm to the left of you - that is a powerful choice.
It ripples out and lets you make even more granular distinctions, that are even more powerful.
By being meticulous, you reduce but you also strengthen. Because every choice to get to that granularity tells you more about your mission, your aim, your goals - yourself.
Staying general. Highlighting every quote in a book. Saying yes to all oppertunities that fit your skillset. You stay safe and undefined. Useful for casting a wide net and gathering mass experience, IF that is the concious choice you are making.
Unconciously made though is directionless. Saying what NOT to be turns you from a weak nothing into a focused something. And you actually do more by making this commitment too...
Saying NO to choices you would have made before becomes easier - this is because you have a well defined value heuristic now, a clear set of guidlines to operate from.
Because of that, your time is focused, your processes clear - your time is less diluted with the 'okay/good' and filled with only the 'great'.
So you need these heuristics.
If you do not choose, life will choose indiscriminately for you in the form of whatever the hell comes your way - since you have no filter to prioritize and disqualify with you say yes to everything.
You can live your life like this. But people who purposfully live like this are making the clear choice to say NO to specialisation.
They know what they are not...