You can't because humans have emotions. People will play timid defensive moves that are bad because they are scared of a percieved threat or overambitious attacking moves when they get excited. A chess engine has none of this human intuition because it's just a calculating machine, it searches huge amounts of variations and determines the best technical outcome.
Chess engines that have their strenght lowered to mimic human players are just designed to sometimes play random bad moves. When a human player makes a mistake it's because they misunderstood something strategically or missed something tactically in the position. However, against a computer these bad moves don't come from errors in reasoning because a computer doesn't reason to begin with. This makes their mistakes completely artificial and you can often tell when the engine makes a funny unhuman move.
When you beat an engine it's because it chose to play the losing moves, where's the fun in that? :P
Ugh you can clearly tell when I set my chess engine (Stockfish) to a level, it makes perfect moves everytime. So I set the strength down to like 16, and that's still a lot. I guess my question is, how do I make a chess engine (even other than Stockfish) play more humanly?? How do I make it not as aggressive, but make it play more tactical?