As someone who has been a young, successful entrepreneur and is fast-becoming a middle-aged one, 3 weak habits come to mind.
The first weak habit is blowout.
Young entrepreneurs, especially if they become successful early, put a lot of pressure on themselves and this results in a blowout in time off.
This is the phenomenon where they will work crushing hours for 2 weeks straight and then use that to justify a ski trip for a week to "decompress".
If they just took proper breaks and care of themselves, this would be unnecessary.
The second weak habit that happens with young entrepreneurs when they hit success is that they scale their lifestyle along with their business. They literally spend money faster than they can make it.
To be fair, I believe that every entrepreneur goes through this. The first time you start making more in a week than most people do in a year, it gets to your head a bit and you want to enjoy some of it.
My advice there would be to get it out of your system as fast and as early as you can. Realise how stupid it is and start to do smarter things with your money.
The third weak habit is believing that the adults know more than you.
Some do, but many don't.
Listen to the advisors you trust, but if the business advice you're getting sounds a bit off... don't be afraid to disregard what someone says, even if they're 20 years older than you.