So you want to be a solo traveler…
You need to make a choice: do you like sleeping or do you like having your things?
Solo American travelers in Europe are going to be robbed at least once a day. Usually by the third or fourth time you won’t be able to travel anymore and you will have to wander around the city and find the U.S. Embassy. Don’t be embarrassed 3/10 American Tourists end up at the U.S. Embassy at some point during their trip.
If you still want to be a solo traveller, invest in some bungee cords and locks. Wrap the bungee cords around your biceps and thighs, then padlock them to your items. This will at least greatly inconvenience your muggers.