Too Jealous for Polyamory
Focus less on emotions you don't want to experience and more on the actions you take when you have them.
What if I think I'm too jealous to handle polyamory?
Jealousy isn't a state of being. It's an emotion. It's not something that we purge from ourselves. It's not something we can eliminate with the right mindset. You're not a jealous person any more than you are a sad person, happy person, angry person, etc. I would avoid defining your entire being by one state of emotion, even if you do struggle with one more than the others or if one feels more unpleasant than the other. Defining yourself in this way is resigning yourself to a state that isn't fair to yourself.
Instead of focusing on the emotion you don't want to experience, focus on the actions that you feel this emotions cause you to take and how you can shift that. Jealousy is something you may feel regardless of how emotionally secure you are. A lot of people make the mistake of believing that if they do all of the reading, or what I call the Polyamory PhD, they will somehow be able to prevent themselves from negative emotions.
It's like reading for 6 months about music theory and expecting yourself to be a virtuoso when you pick up an instrument. I have said in my polyamory 101 and polyamory 102 articles before that "a relationship is not a skill" and it really isn't. But learning communication, negotiation, implementing boundaries and relational skills are often built in relation best. They can't always be learned purely through theory.
So rather than asking "What if I am too jealous?", ask yourself what it is you do when you are jealous and why. What does it mean when you experience jealousy? What is the story you are telling yourself? What do you expect of yourself? Managing your emotions will be much harder for you if you use them as a yardstick for whether or not you're "good at polyamory". Expect that you are going to feel strong emotions and see what you can do to manage them.
For people new to polyamory, I don't think the main concern is actually strong jealousy or emotions, because those are expected. Ask yourself if you are okay with getting less time with a partner than you would usually get in a monogamous relationship. Could you be monogamous with someone who has a time intensive career and didn't have a lot of time to spend with you? There are people who have no problem with their partner dating other people, but would struggle with the lack of time they would get with their partner.
If you would otherwise be comfortable with that, then I would focus on trying to understand your ideal management of time. How much time do you want to spend with how many partners? What is your ideal and how can you negotiate that with others?
If you are currently partnered and opening up, then I would suggest you immediately begin having dedicated time together and dedicated time apart and not just falling into spending all of your time together because you already have. My 101 and 102 articles previously discussed will go through some of the basic things that will help you figure out the basics of emotional management.
I hope this helps and good luck!