You sound a lot like me when I was finished with school. I'm in my late 20s (and you're in your early 20's?). I used to read a lot of books back then and had friends that were older, like in their 50's or so. I think I was searching for answers for a long time and trying to be the best person I could be. I had a lot of questions on my mind about everything. I even befriended some of my professors and would visit their homes and talk with them. But then I realized they were people with their own issues, and in some ways, they were less mature and strong than I was! So that didn't work.
But from one ISFJ to another, I would say this:
*Other people's experiences and insights are interesting and can be inspiring, but in the end you'll want to trust your own judgments foremost and draw your own conclusions about things. Don't hold other people's opinions higher than your own.
*If you have a compulsion for self-improvement like I did, it's better to stop and work on self-appreciation instead.
*It's good to think about and be prepared for the future. You don't want to lose sight of it. And time is always moving forward though it doesn't feel like it is. Situations change, people are lost, lots of things are temporary. Even close friendships don't always work out though you intend for them to.
*Develop a healthy amount of skepticism. Don't trust people and be generous towards them right away if you can help it. (This was a huge lesson I had to learn..more than once.) If you have a soft spot for wild types, keep an eye out on their character even if they are a loved one. Don't be unconditionally understanding towards them.
*Make it a priority to find things that are enjoyable and fit them into your life. Seek out pleasures. Having fun should be as essential as bills and laundry, etc.
*When you're feeling very, very upset, let a trusted person in on it. Very difficult to do, but it helps.
*I love the idea of lifelong friendships, and in the back of my mind, it's what I tend to strive for, but it doesn't always work out that way. Some friend(ship)s get to be lousy over time. Though you may already have a small circle of friends you're committed to, keep an eye out for new people you might hit it off with too.
*Admiration and appreciation are hard for people to express. Just know that many people feel that for you though they aren't saying it. They're saying it to each other, but not to you.
*In a couple years, you'll be nicely surprised at how confident and comfortable you feel with yourself. Lots of things won't feel like such a big deal. Shyness and assertiveness get better too if you struggle with those.