My first experience was my grandfather (my mother's father), when I was 13.
My grandfather (my mother's father) used to do his Friday prayer at my school mosque. Somehow, after he had departed for several weeks, I completely forgot about him not being around anymore.
I sat on the lowest step of the mosque staircase from the time when the prayer ended (slightly after lunch), until about 3 pm. Then, it suddenly hit me that the person I was waiting for would never come out of the mosque, no matter how long I waited there..
I went home holding back my tears.. and when my worried mother (there was no mobile phones yet around that time) asked me why I was so late coming home from school. I lost my voice for a moment, before I choked while answering, "I was waiting for 'Eyang' (grandparent in Javanese language), until I finally remembered that he wasn't in the mosque.."
I could see my mother's eyes suddenly were glassy with tears, but she tried to hold back her tears to give me strength and she tried to smile as she hugged me tight, "Poor girl! It's alright.. Things like this happen to everyone. The most important thing is that you are safely home now."
Ah, I still miss my grandfather to this day.. and my memory of that day stays with me forever..