1. If you want to have kids, do it sooner rather than later. The sooner you have them, the better: they grow up so fast, you'll still have time in your 40's to enjoy life with them as teenagers, if you're lucky. If you leave it too late, you'll be pretty disconnected from their teen lives, and hell .. what 40-year old doesn't enjoy the odd jaunt with their teenage kids, eh? I know I wish I'd had my kids a decade sooner .. and don't let anyone tell you its hard, either. Its not hard, if you love them enough, to keep your lives together and do well as a family. Family units are the strongest groups you will ever find or belong to, if they are indeed a unit ..
2. The wisdom of the Mob. It doesn't exist in nearly as palatable a form as most people might desire, and there is also the ugly truth that the Mob can be downright stupid. Collective truth is often full of lies. You would be wise to exercise your ability to disassociate yourself from collective thought as often, and as early, as possible. This means, always question "what everyone else knows to be true" four, five, six times, before you use it as a basis for life decisions .. The Mob wishes to Eat you, Individual, and Never Forget That!
3. Save. Save, save, save. 10% of your money saved on a regular basis now is a huge relief in the future. I wish I'd enforced this on myself a bit better in the 20's .. you simply cannot avoid the fact that if you save during your most productive years, your least productive years will be better off for it ..