I've often said to my local Mustachians and family that FI/RE isn't a life purpose at all, it's just a means to enable you to fully focus on your life purpose. So let me provide some input that you do not find touted much on this site or in culture, and you can take it or leave it.
I'm just going to attempt a sequence of reasoning that may help you figure out what you are lacking and why.
At the end of your life, you get to take nothing with you. No money, no items, no experiences. If you get to have everything you want, have any experience you want, do nothing but things you think are fun, you will reach the end of your life still empty because you'll be leaving it all behind and wondering what the purpose really was. Now, if we're all a bunch of evolved biomatter/space dust, then the truth is your life has absolutely no meaning and regardless of how you manage to stimulate your senses, whether you do good or do harm to any other organism is absolutely meaningless and your only focus might as well be to figure out how to most satisfy your sensual desires for the duration of their existence (if they can be said to exist, and if desire can even be considered an accurate word) and to prolong that existence if you find any value in doing so. You can attempt to rationalize things some other way given the current state of "evolution" and species survival and the herd or whatever you like, but in the end none of it matters, even the survival of the human race is nothing except a random sequence of physics and chemistry that doesn't matter. If this is, indeed, your stance, I probably can't help you. Follow the other advice here and try to figure out what stimulates you and attempt to find some kind of satisfaction in it. I can give you a book's worth of argument for why none of the above makes any real sense when examined rationally and carefully, but we'll leave it abridged.
Now, the alternative thesis to the above is that there is a God who created everything we are and everything we experience. If this is true, then the ultimate objective which would bring ultimate satisfaction to our lives would be to live our lives in a way that is as close as possible to what he intended. And if this is the case, then our primary objective in finding meaning should be to figure out who he is and what his ultimate desire is for us. I could go into another book's worth of content on how to come to the logical conclusion regarding who God truly is and how we can know, but again, let's leave this abridged.
In summation, I have learned through the course of my ~30 years of life that the most rewarding things you can do, and the only things you will truly find satisfaction in on your deathbed are what you did for others -- acts of love and selflessness. I have known since before aiming for FIRE that my goal in life was to love God and to share his love with as much of the world as possible. Tangibly, this translates into a desire to spend as much of my time in this physical life as possible serving the poor (in both finances and in spirit) and rescuing those in oppression and bondage (specifically victims of sex trafficking) because I believe every one of these human beings has a soul which is of infinite worth individually. It's not just about some collective good, because the "collective good" doesn't necessarily do any one person's soul any good; each person matters on an individual level, and their experiences and desires are all unique. I want to impact as many individuals in a positive way as I can during the course of my life as possible and FIRE is a fantastic way to shed 40+hrs / week of distraction to focus exclusively on this objective no matter what it requires. My pre-FIRE goal is to make my career double in achieving this objective as much as possible while I still require the income (in practice, making money when focused on helping those in need [if the job isn't government subsidized, which I do not want, because those positions restrict your ability to truly be able to do what you believe is right and important] is difficult and to do it full time is generally to forego the ability to make any significant money). But all my FIRE objectives and principles of minimizing meaningless excess are completely in-line with my overall life mission; it's perfect harmony.
So that is the short answer from my perspective -- that you won't find satisfaction in anything until you understand the true context of your life and what it really means, and that should be your first focus. Keeping distracted with pleasure or occupied with tasks is counterproductive until you know where you're headed. I'm not going to turn this post into something looking like a "propaganda" brochure, but feel free to message me if you'd like some resources for logical minds that can help point you in a direction that makes sense. Over the last few hundred years there are countless examples of well-reasoned writings from intellectual giants that step through this ultimate question of mankind in the most logical way possible that I find very helpful.
I definitely wish you the best in your journey!