I use the keyboard almost exclusively, and even had colleagues remark on it rather impressed about it I guess (I don't mind the hacker cred, let's be honest here). I never had to force myself, or try silly tricks to drop a habit. I just found myself in situations where either there was no mouse, or it was more convenient to use the keyboard.
First I was forced to use runlevel 3 only, for three months (gpu died and I didn't have any money). Then I had a long commute with only a wimpy netbook with Fedora ...14, I think? With Xmonad on it (because it's damn light). Then I had a job that was done best over a network with powershell and windows remote. Then I had to do a lot of text processing and it was best done using Vim [1]. Then I spent a year on Z/Os where you can use a mouse but the point-and-shoot fields are much more convenient most of the time (except for copy/pasting, strangely). Then I noticed the Windows' 10 tiling desktop manager and there was much rejoicement (it's gotta be a deliberate Xmonad ripoff!). And now of course Windows has a bash shell so there's never any reason to leave the command line. Yay!
On the other hand, it's true that prolongued mouse use hurts my wrist and I am a bit worried that I might get RSI in the long run, so I'm conciously keeping my keyboard habbit fed. I guess what I'm saying is that the main thing you need is a good reason to drop the mouse, rather than a silly carrot-and-stick approach.
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[1] There I did force the issue a bit. I could have used Notepad++ but I was impressed with how a colleague was using vim and I wanted to use it too, so I resolved to make it my main text editor. Then again that's just more of the same: to learn vim I used vim in my everyday work.