Love itself is very sweet, it maintains the existence between two men and women. Lovers' smiles, joys and sorrows all affect you. Whenever you do something for your lover, you will feel very sweet. With him, even if two people just chat, just watching TV there will feel very sweet.
But if you meet the wrong person, love will be very bitter, and every minute and second with him is suffering. He doesn't care what you have done for him. He feels natural. In the long run, you will find this love very tired.