I always take my cell phone, some money and my identity card (cause it can be used as my health card in emergency cases),sometimes I like to take one or two energy bars and my lip balm. And that's it!
You should also take spare tire and, of course, pump. I don't take it cause my darling has it always with him, and we usually ride together on rides that are longer than 50km.
"Life is not measured with the quantity of breaths you take, but with the quantity of moments that took your breath away..."