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Heartbreak is painful and every pain needs time to heal. You can take a time off but never mourn forever. Whoever broke your heart has moved on with life.
Never start a new relationship until you are fully recovered from the agonies and pains of the last one. Starting a new relationship immediately can make the new person miserable because you might end up blaming and punishing him or her for the sins of your EX.
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Not everyone likes to go to jail for another person's offense. It's hard to function properly in the PRESENT if you're still holding on to the PAST. Make sure you are totally done with your EX before going to the NEXT.
You can never be physically present in two different locations at the same time. Always close an old door before you open a new one. Be open but don't be loose, be very careful how you talk about your EX in front of the NEXT.
Talking too much about your EX means you may have an unfinished business with your EX and this can make the NEXT to never take you seriously. Avoid bringing an old drama to a new relationship if you truly want peace of mind.
Everyone want security in their relationships, unnecessary communication with your EX can bring insecurity to your NEXT. Insecurity brings doubt and when there's doubt the trust becomes a problem.
A relationship without trust is like a ship without water. You can only sit in it but it will never take you anywhere.