Become a more productive [computer user] (insert Developer, Excel Programmer, Word User, Internet Surfer....).
Every time you want to do something that involves taking your hands off of the keyboard and going for that damn mouse, see if what you're about to do has a keyboard shortcut. Use the mouse if you have to to find the shortcut (sometimes they are displayed next to the item in the menu entry), but don't use the mouse to perform the action, use the shortcut instead. Next time you want to do the same thing, you'll remember the shortcut instead of the reaching for the mouse.
Result: you'll be much more productive without the mouse.
It's not a question of getting 3 minutes more out of the working day. It's about not breaking your flow of concentration and at the same time improving your memory, and none of us are getting younger...