If your ex is reaching out to you, what they are reaching out for is the green light.
In the Great Gatsy, he ( Gatsby) was trying to reconnect with his ex-girlfriend because of nostalgia for the moment he intertwined his sense of destiny with her. In like manner all those beautiful moments in your past relationship have formed the green light that your ex is reaching for and is hoping to relive.
But the reality is that time changes people. You are not the same person you were before they broke your heart. How can you possibly hope to return to that version of yourself? You can't and in like manner your relationship can never be what it once was nor can it be made better. Trust me in this once a relationship is broken it's best if it remains so and is never revived.
Do not be like me or Gatsby trapped in a viscious cycle reaching out for the light that is long behind us. More importantly do not let your ex back into your life if you cannot keep them in the bounds of friendship.