This is what I do.

Also, don't be afraid to be stubborn and set in your ways. It really helps to own only one of something (one purse/backpack/tote, for instance) and always use it. Have a spot where you use your laptop and always use it there. Refuse to buy expensive and fragile things most of the time, and if you do buy something fragile get a case for it and a special routine for protecting it. If you're frequently losing/breaking things, that means you're not used to devoting mental energy to your possessions; so you should reduce the amount you need to think about them.