Have you had a friend who gets jealous easily? Worst still if it is your partner. Your girlfriend or boyfriend maybe.
People who get jealous easily, want all your attention on them. They will get angry if they know that you treat other people the same way you treated him/her.
To you, you are just being fair. To them, you are being unfair.
"You treated her for movie next week? You always do that do you?" (Wondering what is my position now...) ~ and its obvious he's treating the girls as friends only.
There's no need to be jealous. Especially when you know that the man is still single and available and he is NOT lacking of suitors. Just be glad that he dated you once... you know how it's like to spend some time with him.
We can't always eat our cake (ohhh..I hate this phrase). Sometimes we can't afford to buy the cake, sometimes we got it but we can't eat it, sometimes we can only taste a little.. There's no perfection, expect the unexpected.
EXPECT THE UNEXPECTED