Well if you are in your 20s and don't have a lot of experience, you might want to hire some consultants with experience to guide you. If you have venture capitalists you want to listen to their advice as well. Don't make an excuse that you are young and don't have experience and the opportunity cost is it eats up your younger days. You can't be a Lone Ranger, you need to be developing a team, a diverse team of people with different backgrounds and different skill sets. Don't limit yourself to just people in their 20s by the way.
I spent my 20s and 30s writing software for companies, inventing new things, and having managers taking credit for everything I did. I expected pay raises and promotions, but those went to the people in the managers' social kliqs who had people skills (bullsh*tting, backstabbing, drinking at happy hour with the rest, gossiping, schmozing around the office instead of working, watering office plants, making coffee, etc.) instead of technical skills (developing code, coming up with new ideas for inventions and software, writing documentation, debugging, knowing how a computer works, knowing how to do research analysis and design, quality control, keeping up with trends via Hacker News and other sites) and my problem was that I was too good at the technical skills and I had to go. So I was 'used' to get to 'goals' and once those goals were reached I'd be fired and then find work at another company where it started all over again. Until the stress of it all made me too sick to work and I ended up on disability. (Programmers are a dime a dozen these days, we get 500 resumes a week for your position and we can hire a programmer for a fraction of your salary that won't get sick on the job!)
I guess I should have developed some 'people skills'?
Anyway now that I am in my 40's even if I was well enough to work, nobody would hire me, I'm too old. I have dual degrees in computer science and business management, but it just don't matter anymore.
The second myth, yes you need to focus on more than the business. My mistake was not focusing on my emotional, physical, and mental health and I got really sick doing my "balls to the wall" software development and focusing 100% of my energy into my job. Always keep a backup career as well in case software development or whatever doesn't work out. Find something you love to do and turn it into a hobby, that you might be able to turn into a business. Or else if you don't love it you might hate it and it makes you sick anyway.