Having being on the other side of mediocrity, first thing you'd realize when you decide to change your life, is that your life had been a mess all these while because of lack of vision. No aspiration, no goals.. Just you, throwing darts in pitch black darkness hoping to hit the bullseye.
When you don't know what you want or where you want to go, anything will be "OK" for you. But sooner or later, you'll realize that "ok" is not what you really want. If you don't, life has very elaborate and intricate ways to make you come to that realization. Some will see it and make amends, others will live in denial and blame, till their last hour of existence.
A life without vision is a very hard life to live.