Let me start off by saying these qualities are not only achieved by skateboarding, these are just some things skateboarding can help you develop. Also, this all opinion based, some of you might disagree.
Fearless/confidence:
So, this one's quite obvious, but skateboarding makes you worry less about the feeling of pain after you mess up a trick. After a while of skating, your mentality starts to change. You start to invision how you want the trick to be landed, and you start to lose that fear factor that prevents you from progressing. Once you have faith in your muscle memory, you gain a feeling of confidence, and you don't get those ridiculous thoughts about severly injuring yourself, or accidently bailing out and landing weird.
Determination/(Trial and error):
Have you ever played a sport or tried to learn a hobby? Ever hear that one saying "Practice makes perfect"? Or "Keep trying until you get it right"? The goal wasn't to make you perfect, it was to keep you determined, and to help show you what you can accomplish if you just keep trying. Progressing in skateboarding is souly reliant on trial and error, which also pushs you to commit more to the task at hand. I like this concept because it can be applied to anything, if you keep trying to make that 3 pointer you will, if you keep trying to make that touchdown you will. Failure is not a bad thing, because when you do succeed, and the more you do. Your mind will calibrate the difference between failure and success, this is where your muscle memory comes. This is what makes trial and error so effecient, the more you build your muscle memory, the less thought and effort you will need to complete the task, thus at the same time making you better at the skill. The beautiful thing about trial and error is you don't need talent, you can know absolutely nothing about the skill, and still become an expert at it.
Agility/balance/stamina:
Yes, i had to include the most basic qualities, yet they are more important to the bigger picture. The more experience you have with these skills, the greater ease of learning you will have. I know these skills seem obvious, but most people start skateboarding without these skills. But, then come to find out a few months of skateboarding later, how much their skills actually increased. Honestly, these are the hidden skills you don't even realize that all that practicing helped you develop.
Moral of the story is, (i know its cheesy) but DO NOT give up. Giving up is the worst thing you can do, even worse then utterly failing. Imagine a diamond miner, he's mined down this mile long underground tunnel. He is so discouraged because he worked three ten hour days mining this tunnel, and hasn't uncovered one single diamond yet, so he decides to give in to his fatigue. Little did he know, there was 5 inches of rock between the end of his tunnel, and the biggest diamond cluster ever found. It just goes to show how giving up is the worst thing you can do to yourself.
Fear can also be what's seperating you from success, i cant stress how important being a little fearless can be. For an example, this little gap between two ramps made me shiver in my boots, the gap looked way to big, even for my level of skill. So i procedded to watch people ollie this gap every single day i went to that skatepark. Until one day i was fed up with some small emotion holding me back. So, i just went for it with the mentality that ive done it a millions times before. Come to find out, in my opinion it was the easiest obstacle at the park. Don't be afraid to push yourself, it is all a mental game, its up to you wether you want to be in fear, or have a level head.