I consider myself fortunate for having learned this early, but for me, the biggest lesson is that 30 is NOT the new 20. Our 20s matter, and the decisions we make in our 20s can profoundly influence our futures.

"Oh, you have plenty of time to figure it out. Don't worry about anything," people say. On one hand it's true that most of us have time to kick back and relax a little more than we do. But on the other hand, life is definitely short. That means there isn't a lot of time to waste on dead-end decisions, at least not if you value having a life that feels at least somewhat focused and controlled. Not everyone agrees with that, but I believe this strongly. There is no greater sense of loss in your 20s than feeling like you don't have a plan and aren't on your way to somewhere you want to be. With that in mind, I try to stick to the following principles:

• Who you date matters. In your 20s it's tempting to date people who you see no future with, and to spend time in "fixer upper" relationships because they're fun. But this is a bad idea. Become your best self and do what you have to do to attract the highest quality partners, and maintain the highest standards every step of the way. When you approach 30 and start to think about settling down, you don't want to feel like you're settling for less than you want, and you don't want to be in a position where you're having to do last minute work to reinvent yourself to increase your dating market value either. If having a family is important to you, plan ahead for the life and type of partner you want and position yourself accordingly.
• Move quickly when you get the sense that something isn't right in your career. One school of thought is that you should be thankful for any job and stick with it. I disagree with this philosophy, unless there are other people who you are responsible for supporting. In your 20s there is relatively little cost/risk to pulling up roots and relocating, or restarting your career in a different direction. Do this fearlessly and immediately.
• Surround yourself with people who make you a better person. Don't tolerate people in your life who exude negativity or an unhealthy lifestyle, or have a complacent attitude about the future. They'll hold you back and encourage you to waste your time and energy. "You are the average of the five people you spend the most time with." That's true with regards to income as studies have shown, but in my experience it's also true for character, integrity, and happiness as well. Choose wisely.
• Be careful who you take advice from, or at least be aware of their biases and motivations for steering you a particular way. So many people will try to tell you what to do, and it's tempting to listen to people who don't know what they're talking about just to have some direction. But whenever someone offers me advice, I ask myself, "Does this person have a life I would want for myself? What is their family like? Do they seem happy? Do they have good friends? Are they healthy? Do I enjoy spending time with them? Are their lives together?" If not, I ignore them and find a better role model.
• Follow your gut. You can rationalize any sort of decision these days and find a convincing article somewhere on the internet to support any idea you have. Ultimately, your heart knows where you're meant to go and what is truly important to you. Simplify your life by letting it have the final say.