What is the ruling on feeling longing and regret over the separation from a foreign girl after breaking up with her due to a reawakening of conscience, and does this affect repentance and commitment to acts of worship?

It would have been more befitting for you to regret your dereliction concerning Allah's right and your disobedience, rather than yearning for that woman. For yearning for her contradicts the sincerity of repentance. Fear Allah and repent to Him with sincere repentance. Seek a woman of good character and religious commitment who will assist you in obeying your Lord, and hasten to marry so that it may make you forget what has passed.