First of all, you're going to be fine. If you're thinking this way now, your instincts and predisposition are working in your favor. So relax. If you're making X today, 20 years from now you're going to be making 10x. But don't rely on that.
Whatever your making or spending, pay yourself first. 401k as much as you can, but no less than what earns you your full employer match potential. What's left over is your income.
Now, this part isn't hard- i can't express this with enough emphasis how important this is, talking lifetime important- but takes a dedicated 15 minutes. Open a brokerage account and set up a secondary direct deposit to it. Pick a number, any number- $20, $500 - and have it go straight there. You now have a widget in place you can modify within 30 seconds. But do it smartly. Next, Figure out what your monthly expenses are, add a little bit; then update your widget to send everything else to the brokerage account.
Now you can live to a monthly zero balance in your checking account. Your savings is on auto pilot. Your bonus goes to savings, your raises go to savings- get it?
Now you need to enjoy your advancements, bonuses, etc. For real, you do. But now it's a conscious decision as to how much you want to roll into lifestyle vs a decision how much to peel out to boost savings.
The early dollars you stash away and invest (what to do w it is another topic) will have more pulling power over your wealth generation phase of life than you can ever imagine.
So let's say your making 60 (no idea what grads make out of school today), you take home 40 post 401k and taxes. You've got 3300 or whatever a month to play with. Funnel 100 to fidelity account per check. Next year you get a $100/check raise, bump the 100 to 150; get a 6k bonus, force yourself to transfer out your treat. The mindless contributions will build wealth and the deliberate withdrawal activity will force you to really consider the value of your potential expenses.
Lastly, don't get cute- total market indexes. There's so much money in the system, and it ends up in the market- just be happy to be in the game and you'll be fine.