In my opinion there is not a fine line between missing someone and being glad you dealt with them, but happier they're gone. Let me be very clear, I said REFLECTIONS upon being asked are what's acceptable not MISSING their presence! If you're missing that someone while dealing with another person maybe you're not quite ready to move forward. Let's review some definitions to make sure you understand the difference.
MISS (noun): A disadvantage or regret resulting from loss.
REFLECT (intransitive verb): 1. To think quietly and calmly. 2. To bring about a specified appearance or characterization.
Did you read that? If you thought you missed them can you now say it out loud after seeing they have you in some sort of disadvantaged state? If you still say yes you need to make steps to either resolve the issue between the two of you, or move forward for your personal well being.
If you, like myself, can truly say you can realize personal growth as a result of a past relationship then you my friend are a confident reflector. You realize that denying the positive impact on your life by another human being is pointless, but you can truly say you don't miss their physical presence in the current stage of your life. You have embraced the fact a relationship has ended but the experience was beneficial. I'm here to tell you not to deny that someone has enriched your life in one way or another in spite of the context of the relationship. It may have been imperfect, unconventional, or even forbidden but it managed to bring some sort of enlightenment to your current state of mind and outlook so don't wish it never happened. Hold on to my aforementioned point that loving someone doesn't mean you're supposed to "be" together.
All experiences in life and love should be turned positive so they are absorbed for your personal improvement and not your emotional demise. And it's okay if you need someone to talk to for guidance through that process! Past relationship achievements can sometimes make the person you are currently involved with the recipient of some exceptional behaviors. Just be sure to provide positive reinforcement for the person you are now liking and learning to love and reassure them of the position they currently hold in your life. If you want to keep it hood and grimy we could sum this all up in a few words, "Don't chase them replace them!"
Just today's thought...Thanks for reading!