The way I keep from leaving my laptop anywhere is to put my car keys in the laptop bag.

Barring rides with other people and mass transit, it's impossible to leave your car keys somewhere. And if you travel mass transit, you could leave your wallet in the laptop bag instead. But even if you do travel sans car, you will notice your lack of keys/computer the second you get home, instead of figuring it hours or days later when you try to use the computer.

I do this trick with things beside my laptop, like if I'm helping move furniture and don't want to endanger the phone in my pocket, I make sure my car keys are one of the things I remove also. If I'm somewhere else, and there is anything I might leave, my keys are with it. (And this rule also requires that all of my things are in the same place, another good rule in general.)

I also do this at home, in a way...I put things I need to remember to take with me on top of my car keys, so I can't take the keys without picking that thing up. (This is obviously not a good plan if you can't keep track of where you leave your keys at home, as it will make them harder to find. But I don't have that problem, I only have one place they ever get left.)