Love with wisdom is bliss. Love without knowledge or wisdom is pain.
Why is there pain in love? That is what you are wondering or questioning about!
It is not love which is giving you pain. If it is just purely love, that means you just care for someone, you want the best for them, and then there is no pain.
But when you want something in return from them or you have demands from them, then there is pain.
Small things like you love somebody and they didn’t smile at you, that is enough! You love somebody and they are interested in someone else, they flirt around or complement someone, good enough for you to burn the next 24 hours or days. Jealousy, hatred, greed, arrogance and attachment are all love’s distortions.

That is why knowledge and centered-ness are so important. If you are centered, you can handle all these distortions, they come for a while and they disappear.