The present simple grammar form is actually crucial here.
You and I are constantly changing so what you did yesterday or even an hour ago (and most importantly, why) can be different now.
Same thing goes for the future. You don’t know why you’re going to do what you do in the future.
Now that’s not to say you need to give the finger to your past and future. What you did and why in the past and what you’re going to do in the future matters. But focusing on it is different to having a healthy respect for it, Who you were in the past was probably different to who you are now, and the future you is also probably going to be different.
So it’s all guesswork.
Self-examination of who you are right now, what you do and why, is how you begin to understand what’s important to you, what you want and who you want to be.
Examine your why and you get closer to understanding your who.