I once went on a trip to the Netherlands by train (from Germany). Several days go by and we wanted to rent a canoe and they asked for our IDs for deposit and to check our age. Then I realised I forgot my ID at home in Germany. My friends were pissed we couldn’t rent a canoe but the rest of the trip I was so afraid someone would randomly control our IDs (for whatever reasons but we were foreigners speaking another language so you never know). On the train across the border I was even more paranoid I hid on the toilet all the time which caused a ticket check with two people as they assumed I didn’t have a ticket and wanted to run off. But after telling them I just have a weak bladder and showing them the valid ticket they just laughed. Didn’t need my ID once, not even while crossing the border, but I was soo paranoid I always check if I have my ID or passport several times before leaving and forgot other stuff like chargers because I was so focused on my ID