If you don't already have a wide-angle viewer, install one in your door. Even if you live on a high floor, don't think your unit is impossible to access from the outside. Some thieves climb or jump from balcony to balcony. When you're out, keep windows locked, and sliding doors locked and defended with security bars. If you're out for the evening, leave a light on, even if you're on a high floor.
Professional thieves can pick out a completely dark apartment from the ground.
If you're keeping any belongings in a storage room, don't rely exclusively on the room's lock for protection. Use a high-quality padlock on your own storage unit door. If any unit in your building has been broken into, and the thief has made off with the lock, you could be vulnerable. With a lock, it's easy enough to cut a copy of the key. And if all the door locks in the building can be opened by master key, the thief could gain access to any unit.