It means that you love the person too much to see her spend her mind-space and time with anyone else but you. It doesn’t mean that you don’t trust the other person or that you constantly feel that she is cheating on you. It just means that you wish you were the source of each of her moments of happiness and motivation.
Jealousy helps you truly identify your feeling for the other person. I would caution though that jealousy should be taken only as a feeling. Just as any other. It shouldn’t cloud your thinking and make you unsure about her. It shouldn’t lead you to curtail her freedom, imposing and suffocating her. You just need to deal with this feeling to mature and grow as an individual. Remember that we all have very strong inherent animal spirits. Everyone wants to be an alpha male. That is how we’ve been conditioned since ages – to run the fastest, to hunt the best, and to fight and survive our winnings. However, life is a constant struggle to grow out of that traditional self and act with maturity and intelligence.
The more you get exposed to the feeling, the more adept you become at handling it. The next time you will tackle it better than you did in the past. And yes, there will be times when you will snap. Any feeling, including Jealousy, might get better of you. That could be God’s way of telling you that you’ve done enough and you are losing your humanness in suppressing or in dealing with that feeling. You take a judgment call then. But, for rest of the occasions, it is just about learning to live better.