I'm on my summer hols.! yet i don't fell mentally right. why? Has anybody got any good relaxation techniques?

I finished school for the summer hols yesterday. Usually I get a great buzz from being on holiday, yet I just don't feel that buzz. I feel really down and kinda depressed except i don't know why! I'm going into my second year of high school next year (I'm 13) so I'm not really sure why finishing the last term of school for this year should make me sad? The only thing i can think of is that i'm not going abroad because my dog had a cancerous tumour removed and the vet sed she was doing well if she lasted three months so we don't want to be away if the moment comes. I'm tired as well and I don't know why either? I'm on a Hypnotherapy course of two cd's (Stop Worrying and Relaxation and Self Confidence Building) I haven't listened to either of them in quite a while should I be doing that? I feel almost depressed what should i do? does anybody have any good relaxation techniques that will help me? Please Answer