(Trigger warning: this passage may stimulate a trip down to memory lane. Read at your own risk.)
Rejected by a potential lover?
Broke up with someone dear to you?
Heartbroken over your favorite group's latest dissolution?
It's not okay but you have to deal with it by moving on because:
This is when you learn to adapt and accept things at their current states;
This is when you know your limits, and;
This is how you attain self-actualization.
Move on because you can.
As long as you have goals for your future and a healthy body, you are capable of moving forward and chasing your wildest dreams.
Don't leave your plans behind for an untimely commemoration of a past event.
You alone are capable of change.
Move on because you need to do so.
Time is ticking, hence deadlines are nearing. (Most humans I know of are quite preoccupied with their own lives).
Being human and all, you still have humanly preoccupations that need your devotion.
Control your emotions before they devour your consciousness in entirety.
Why not designate a time frame when you can grieve all you want to?
Alienate yourself from human contact for a while.
Use the time to rejuvenate the senses.
After that, refrain from contemplating about the past.
Then, make an oath to never cry for the same reasons again. Don't let the former heartbreak affect your odds of reaching your goals.
I'm not telling you to totally forget what had happened; I'm telling you to get up and thrive while applying what you have learned from your heartbreaking experience.
For future's sake, that was the thing of the past.
Walk without turning back.
Move on because you deserve better.
By experiencing a heartbreak, you have considered yourself warned and experienced.
Consider yourself a success in unleashing one milestone: you have learned.
You have the gift of knowledge (which costed you a heavy price and that was despair) that you can share at the disposal of the inexperienced.
Move on because you don't deserve to be stagnant.
Move on because you can make your life more interesting than it seems today.
Move on because you always have a chance to improve.