What or who are we willing to sacrifice today in exchange for a supposedly better tomorrow?
I would frame this different to think about delayed gratification or as Bitcoiners refer to it; low time preference, do things for your future self and being able to think about your long term. Good habits in your 20's and 30's will reap huge rewards when your older. I'm 55 and benefitting enormously from just a few good decisions back then. For me, the future of my 20's and 30's is now.
1. Get fit and stay fit
People my age who haven't taken care of themselves lose muscle mass, bone density and strength. Fat around the mid-section greatly increases odds of getting sick. All of those inputs and getting sick (up to a point) are reversible. Lift weights and cut carbs. This will allow you to do what you want to an old age. That's me, yesterday digging line on a wildland fire exercise. 55 is kind of old for that but not crazy old but I keep up with firefighters less than half my age and have a ton of fun. Habits matter.
2. Live below your means.
Be under mortgaged at 15 years, drive Toyotas for 20 years don't buy items that require you going into credit card debt. You'll accumulate money and by the time you're 50, you'll have no mortgage and the optionality to do whatever you want and as the first idea proves 55 (my current age) can still be very young. Being 50, healthy, able to do what you want is a fantastic outcome!
3. Be willing to pay your dues.
Someone close to me who is younger hates that phrase, I love it. In my 20's and into my mid-30's I "paid my dues" professionally until my mid 30's before being able to strike out on my own professionally. Those dues made me a better person, made me more appreciative of what I have and I believe better at my day job.
4. Never say no to an opportunity.
This is about trying new things. You never know where opportunity might come from. Not saying no, led to a couple of lucrative side gigs and experiences I would have never had. Me on stock market television saying not to buy Fitbit.