Myth #4: If one partner is jealous, it means he or she truly loves and cares for the other.
The Truth: Jealousy has much more to do with the person's security and confidence in him/herself and his/her relationship (or lack of security and confidence!) than with love or caring.
You may have tried to assuage your partner's feelings of jealousy by demonstrating how much you care for them. If you've done that, you may have realized that no matter how hard you try, you can't stop them from having jealous reactions.
You can't improve your partner's self-confidence or feelings of security through your efforts alone. Your partner must confront those issues him- or herself. Of course, you should still be supportive while he/she does so.