smile for the camera

When ever i take a picture i have a hard time smiling, It's the thought of capturing moments where i should be happy, but my feelings just won't latch. Forcing smiles for pictures have always been hard for me. The way people always make it seem like its a sell catch. They advertise people always being happy, but what about the ones who feel like they're dying inside. Should we advertise our fake happiness in pictures. Sometimes im confused, I don't want to look back at a sad miserable person, but i don't want to lie to myself. So when someone say " smile big " I try my best to give a great smile, but my eyes always tell the truth.