It doesn't sound immature at all.. You're scared, and that's OK.

You sound so much like me.. I used to try and be perfect for my mother.. And I'd never talk to her or my dad about how I'm feeling because my dad doesn't want to know, and my mum can't handle emotions very well. I've found it incredibly hard to trust anyone because I was shamed so many times in childhood by my parents when I tried to express myself. I haven't wanted to go through that hurt again. As a child, I started to believe I was flawed somehow and tried to compensate for that by being perfect in everything I did. I started seeing a therapist some years ago and she's really been the only person in the world I've been able to trust enough to tell her almost anything. This is probably going to sound sad, but I thought that since I'm paying her, she must listen to me - I was so certain no one would out of their own free will - that's how worthless I've felt because my parents didn't accept and love me as I was. Paying her also meant she couldn't turn me away 'when she got bored of me'.

My guess is that you put up those walls initially to keep people out - the people who didn't accept you, for whom you couldn't be what they wanted you to be - so that you didn't need to feel the hurt anymore. But now, you might realise on a subconscious level that the walls aren't necessary anymore - that if you meet someone today who doesn't accept you for who you are, it doesn't mean you have to abandon yourself. It might hurt, but you can learn to tolerate and accept those feelings without needing to lose yourself.