Do not forget your front door key in the apartment
Sounds terse, but is effective and has worked for me for years.
If you often forget the key in the apartment and exclude you, you get used to the following procedure:
1: Always leave the key in the still open door when leaving the apartment.
2: close the door
3: always lock the door.
After a while, if you forget the key, when you close the door, you will notice that something is wrong and you are not touching it. It really works and has saved me tens of times trouble!
