Jealousy is a natural part of being in a polyamorous relationship for most people. The openness and freedom that various relationships offers can sometimes be overshadowed by hidden fears and insecurities. Learning to manage these feelings around your partner’s other relationships (metamours) can make a big difference in joyously living this lifestyle. Unaddressed jealousy, however, can quickly become painful and destructive- mentally 'driving you crazy' when your partner is with someone else, and potentially ruining your relationship(s) in the long run.
Jealousy can arise if you feel your partner is not investing the same amount of time and effort into you as with other partners. It may also come up if you've been with your partner a long time, and they get excited about seeing someone new and enjoying NRE, or new relationship energy. Making comparisons between you and your partner's other lovers can create a sense of competition that sets up 'winners' and 'losers,' especially when you think you don't rank as high as a priority.
Spending time working through your feelings of jealousy is time well spent. Uncovering your insecurities and fears can open you up to new levels of self-confidence. It may be helpful to talk with your partner if you don’t feel you’re on the same page with the amount or quality of time you spend together. Sorting out unfair expectations from getting legitimate needs met can be helpful as you move forward in your relationship.