Finding the Lock to My Key

I am a 15 year old girl, and I have been struggling with depression for a while now. Last night, my mom and I attended the One Republic concert. 

My mom and I saw the necklace (I wanted it, but I didn't have enough money) and she bought it for herself, but no longer than a minute later she gave it to me. 

My mom doesn't know what is going on or about my struggle with depression, so she just thought it was a necklace that I wanted and would wear. Internally I have put meaning behind it, to me I think of it like this:
I have a key with no lock that I know of. The key is the answer. The lock represents the questions I might encounter. I have all the answers, but I might not have all the questions of problems that life will throw at me yet. 

I am hoping that this will help me stay strong, and eventually get better... Maybe one day this key will show me the answer to being happy again.