I'm sorry Jenny. If he couldn't walk on his left leg, that sounds very much like he could have had a tumor pressing down on the nerves, in that case there was an almost certain chance there was nothing you could do other than surgery, but if it was cancerous it could spread even after being removed and he would just slowly and painfully die after the surgery. I'm not sure how old he is, but they can get tumors at a yongue again even though it's very rare to get them till 5-6 years of age.
He died knowing that you loved him. Its going to be hard to get over the loss, but you will. You're always going to miss him like crazy but eventually the happy thoughts wont hurt anymore, they will make you smile. A new bird will really help the process, I said I'd never get a new bird after Elkie died but I did about a week later and I was still very depressed but Cosmo was such a sweetheart and he helped me a lot. Before getting a new bird I moved my entire room around, put the cage somewhere different and completely revamped it (then got a new one), and made sure everything was for Cosmo now. I was terribly depressed for a while, so was my mom, even my dad cried when Elkie died and I've never seen him cry in my life (he doesnt know I seen him). We were all attached to her. But I promise you it wont hurt so terribly bad forever.
I wish you wouldn't leave the forums, if you do make sure you stay around people or stay active doing things. If you just sit and start thinking you're going to cry a whole lot. I stayed around my parents for a while and made sure I was always busy when I could be. When I got Cosmo I had to take care of him and I couldnt just lay down and cry all day.