ANY HELP WITH SADNESS/depression?

Hello, so today I found out that a person that was involved with my life lot is leaving this may. It came out of nowhere and I was completely shocked. After I came out my shock i felt sadness. I've know this person for a year but had grown so fond of them. I hurts so much knowing that their leaving. How do I get over this just so that I can live my life normally till I get home from school.