We've done pretty well fortunately, a lot of that on account of having good jobs and not frivolous spenders. We've always maxed all retirement accounts and had significant savings beyond that. We've mostly bought cars new, but usually drive them for about 13 years. No drinking or smoking either. No stupidly long commutes, but in one location longer than desirable.
Still, I'd probably tell myself not to get in the habit of eating out too much - gets pricey fast. Not make as many outsourcing decisions (this gets more tempting the more money you make).
Finally I'd tell myself to keep housing costs under control. There is a culture that a home is an "investment". It is actually a really sucky investment, but there are still good times to buy vs. rent. The issue is if you buy into the "investment" BS it is easy to convince yourself to buy something bigger. No, no, no. Keep your housing costs low, whether renting or buying. And this is coming from someone who has by dumb luck done extremely well in buying and selling at the right time as far as real estate goes. Keep your head on about housing, buying is fine but don't use the "investment" aspect sucker you into buying too big a house with all the expenses that saddle it. There is a reason there are few big house rentals - the money just doesn't work out. Stay small as practical whether you rent or buy.
You sound like you are on the right path. Keep up that savings rate.
Oh and standard advice for all unmarrieds - know who you are marrying and have many frank financial discussions up front. Better still know and watch your future spouse for a long time. The statistics are of course uncertain, but finances are a primary cause of divorce (some surveys say a major factor in 90% of divorces). It sounds cold and heartless, but honestly it is a huge thing. Some people just haven't thought about it and you can have "the talk" and be on the same page as you. Some may be a write off from the beginning. If a couple can't successfully talk through this ahead of time it is a big red flag regarding other things they will have to compromise on over time. A spendy spouse or a divorce (or often both) is extremely expensive. On the other hand, a solid relationship with a real partner and communication is an amazing and wonderful thing. Don't buy the BS Hollywood sells you on romance - love at first sight is like buying a sports car on an impulse.
