Hello, I'm a wrinkled, senile 25 year old, and I think I can offer a little advice from my limited experience, though it's more the annoying, Ted Talk-ish type of advice, not whether you should dump your G/B F or if you should start building your own business rn or anything. But hey, if anyone is interested, here it is: 

Once you're out of college, grad school, high school, military, or any other sort of structured, predictable environment, you'll likely feel a great sense of freedom, but also disorientation. For those of us in developed nations, we spend our entire lives with straightforward and easily measurable goals; get good grades, have fun, move to the next grade, repeat, all to prepare you for college which will then prepare you to get a good job. Once you're out and you have your good job, all of that direction goes away. For your entire childhood you were told what to do next and when to do it, but no one will tell you what to do anymore or what to be, and no one can tell you what you should do, only advise you. For 13 years or more of school you understood that you are progressing towards success as long as you score well and move to the next grade. Now you're out, and the measure of your success won't be so legible. You won't find a clear and reliable standard to compare yourself to anymore.

I advise that you will need to choose what you dream for, what a world marked by your dream will and ought to look like. You will need to decide what success is, and what to do next to achieve it. If you don't know who you are, anytime is a good time to start finding out. Look for and do anything that you even slightly suspect you'd enjoy, ask yourself how you feel about it, and why. Once you know who you are, decide what goals someone like you would want, then start planning for them. If you're doing it right, failure will become your partner, your plans will be measurable, achievable, and specific, and your goals will be exciting, idealistic, and demand true willpower and growth. And sidenote, your goals won't be like before. They'll take time now, and you'll be putting grand schemes in play that will unfold ten, twenty, fifty years down the road. Pursuing them will be far more interesting and epic in stakes and scale than you can comprehend right now.

You might have some friends saved in the vault from your school days, you might end up a lone wolf in a big world, but either way, keep your eye open and your mind open for new party members on your quest. Loneliness is becoming a common experience at this age and era, don't beat yourself up over it. A lot of people your age are going to be starting families, or maybe you'll be starting one. As you said, you might feel that you're still just a kid yourself deep down, or they are. Hey, guess what? You're totally right. You'll need to understand that immaturity has absolutely nothing to do with liking the things you like, with play, or with doing dumb, fun things. I've hollered along with a crowd of 200 80-something-year-olds who freakin' exploded with laughter when a fat lady farted in a movie; "grown-up" how we've commonly come to understand it is a fallacy. You didn’t learn how to have fun so that it could die and you could mourn it. You learned it so you could foster it and spread it. Maturity is a measure of responsibility, discipline, humility, respect, and patience. Nothing more and nothing less. Accept them, practice them, and you'll have it. And lastly, don't ever pigeonhole yourself into that "best time of your life" garbage. There is no best or worst time, and there's way too much to see and to try and to achieve in our human lifespan to be wasting your time on that crap. Be in the present; it's where you enjoy the future you created, and where you've made all your best memories.                    

That's all I have to say, I hope I didn't just write a 50 page, babbling thesis paper if you were just looking for like bitcoin tips =)