there is a very famous stanza from soundarya lahari... submit urself to the almighty to help u through the realtionship........ one strict advice is never use this as a tool of revenge against the person u loved or love... but i have heard this mantra to be effective.........
procedure
1. offer sweet ponal or kheer to godess and start reciting this stanza ones a day.
2. you will defenately find results in it.
mantra is:
Attracting of sexes to each other)
Haris tvam aradhya pranata-jana-saubhagya-jananim
Pura nari bhutva Pura-ripum api ksobham anayat;
Smaro'pi tvam natva rati-nayana-lehyena vapusha
Muninam apyantah prabhavati hi mohaya mahatam.
meaning: You who grant all the good things,
To those who bow at your feet,
Was worshipped by the Lord Vishnu,
Who took the pretty lovable feminine form,
And could move the mind of he who burnt the cities,
And make him fall in love with him.
And the God of love , Manmatha,
Took the form which is like nectar,
Drunk by the eyes by Rathi his wife,
After venerating you,
Was able to create passion ,
Even in the mind of Sages the great.
all the best if u find it usefull revert back.