How do I prove to my parents that horses are everything to me?

I have been riding since I was three, but I haven't had lessons in a while, due to a crazy schedule with school, as my parents always emphasized that grades are my top priority. However, I have always wanted to own my own horse. So many people know how i feel. When i see a horse, i don't see an animal. I see a work of art, full of grace and beaty, strength and power, trust and love. I see wonder, friendship, courage. I know people understand this, horsey people out there, you know what i mean. You know that feeling in your chest when you want one, the feeling of longing that makes you want to cry. SHould i tell my parents this? I have tried so many things with my parents, and the answer is always no. How do i make them see I am ready for this? It isn't the money.It's the fact that they have no faith in my responsibility. How can i help them see that this is everything to me?