Can anybody give me ideas on what I should include in my letter of appeal?

I just recently got denied by SDSU because “the number of applicants in my major exceeded the allocated enrollment slots.” I’m guessing that means there was no more space available for me. I’m a Psychology major and as we all know, Psychology is a real common major to have nowadays so they have claimed it impacted. SDSU is my local school and also my dream school and I can’t really afford to move away so I want to appeal the denial letter. I know the chances of successfully doing so are slim but I at least want to try. So can anyone give me any ideas on what reasons or explanations I should include in the letter for why they should reconsider their decision about admitting me? Thanks.