Counsellors and teachers say I'm very mature and smart. Should I listen to them?

It's a little long so be prepared to read. I'm 17 and I have a lot of problems. I'm very shy and reserved and withdrawn. I may also have social anxiety. As a result, I have no friends. It's not so bad because I love my alone time, but I realized I really do have to depend on people, to a certain extent. I've been getting counselling and she helped realize that. My entire life, I told myself I was stupid and I was bad at everything. Recently with counselling I'm starting to realize I'm probably wrong. When I'm there, I pretty much tell her what's wrong with me and what's causing it. I understand my feelings and why I am the way I am today. She told me I could become a great social worker one day. She told me how intelligent and insightful I am. She also mentioned that I'm very articulate, despite the fact I don't talk much. She even joked that I should be in her chair and I should be giving her advice. I'm always comming up with wise little lines that I never tell anyone. I wish I would have wrote them down because I forgot them. They tend to come randomly so I don't really think about it. I really am staring to think I'm intelligent. With the people in my school, it's easy to think like that. I have my strength and weaknesses like any human and I know what they are. Sometimes I kind of feel like an old man. I'm talking about the ones who have been through everything and are good and wise people because of it. I believe a lot of people at school think I'm dumb because I don't talk. In reality, I'm just nervous and scared of being right or wrong. With counselling I'm trying to change that. I guess that's all I can say. Should I listen to them and start beliving I'm an intelligent person?