Jealousy is the emotion most likely to derail an exploration, and also the one with the most potential to deepen a relationship, if you know how to work with it. The first thing to understand is the most freeing.
It is normal, and it is not a verdict
Feeling jealous does not mean you are doing something wrong, that you are not cut out for this, or that your relationship is in danger. It is a normal human response that shows up for almost everyone who explores this dynamic, including people who go on to love it. Much of its power comes from ambushing you. Expecting it, and greeting it as an ordinary visitor rather than an emergency, takes most of the force out of it.
Read it as a messenger
Jealousy is rarely the real problem. It usually sits on top of a deeper feeling: fear of loss, a sense of exclusion, comparison and inadequacy, or a simple unmet need for attention or reassurance. Each points to a different response. Fear of loss calls for reassurance. Exclusion calls for more inclusion. Comparison calls for the slow work on self-worth. An unmet need calls for meeting it. When you can name which message your jealousy is carrying, you can respond to the actual problem instead of thrashing against the feeling.
First aid for a spike
When it hits hard, have a plan ready, agreed in advance: pause, breathe and let the wave pass, reconnect with your partner, name the feeling without blame, and postpone any big conclusions until you are calm. Nothing decided in the grip of a spike is trustworthy. The wave really does crest and fall if you do not feed it.
The counterpart to jealousy is worth knowing too. See what compersion is, and whether you can learn it.