You can't practice mind games on a CPU because they don't have minds. Try to study what situations in which top players condition and punish their opponents and practice incorporating similar ideas into your own play. It's a very vague subject so it's hard to give concrete advice, but a mix of studying good players and trying it against thinking opponents should help.
Now, you can use a CPU to practice with if you pretend it will behave in a human manner and try to fight what basically is an imaginary opponent rather than the actual computer. Look up PP's write ups on shadow boxing in Melee for a better description, but if you're going to go this route turn the AI down to normalish because the new bots are a bit over the top imo
