This is a factor of some kind of gaming addiction, which allows you to keep the majority of users. How to involve the player in the game - make it easy, with a gradually increasing level of difficulty.
If you make the game too long, players may lose interest in it. In order to feed the interest, it is necessary to use short levels, where there will be a lot of any obstacles, secret items, various bonuses. These tricks will keep the player's interest, and increase his time spent playing games.