So, what are the appropriate ways to control one's feelings while still trying to express them but not using them as manipulation?
The best advice I have is to practice communication. The best way to express your feelings without using them as manipulation is to start a conversation in way that's clear that you want to discuss your feelings and that you in no way are blaming your partners actions. Emotions happen, trying to ignore them, even when they may not be rational, sucks. Face them head on, accept them, and ask your partner for support if you need it. Other support like counseling is awesome too.
How to handle knowing you are one part of a partner's life, but that other parts are important (sometimes equally or even more so) too?
I had this problem once or twice in the first year of my polyamorous relationship. I wrote down all the things I was insecure about on post it notes and put them on a poster board, I'd also write down possible reasons for the insecurities, then wrote down answers and ideas on other post it notes (or immediate actions I could take to help at the time). They were positive things I knew or believed, but couldn't remember at times of insecurity. Then, whenever I had a stumble I could look at my board and immediately remember why my insecurities were irrational. Having it in writing helped. After awhile I didn't need the board anymore.
Does this impact your relationship or has it in the past and what are your ground rules for yourself and your partner?
I haven't even been terribly jealous of other people, but the uninvited events part hits a chord for my past self!
Ground rules: Open honest communication. In the past if we've struggled with something we talk to each other about it and work through it together, without blame.
As for monogamish, it may be harder to feel comfortable with if you are already feeling jealous. It may work out to be really beneficial if you can work through the insecurities, or it may backfire spectacularly. I'd recommend proceeding slowly. If I may ask, how exactly do you 'go haywire' when you bring up the mongamish topic? Do you react immediately during the conversation? Or is it more of an enhanced jealousy reaction in the following days or weeks?
The thing is that what I actually most want is to be free of being totally afraid of non monogamy. Like, I know I could be okay with it (under terms that I get to pick!) if my activated terror brain could calm down. Which I think it is maybe going to be able to do! Or, I'm wrong, and it won't be for me, and we'll go from there.
Completely understand this. Even knowing for sure I wanted to try it was still really scary to jump in. SO much societal conditioning to work through before I got to all the comfortable awesome parts! And some of it may hurt. That's ok. In my experience each new 'first' is a little hurdle. Some hurdles are higher than others.
If you are still working through past painful experiences I can imagine it would be a lot harder. Honestly if you find this to be the cause of your insecurity I'd try to work through that first, ideally with a counselor, before adding potentially more complications.
I would 100% rather be free of all my anxiety around this. Because it bleeds into all sorts of other things in the relationship (time apart, friendships, independence) by wanting to control a feeling of safety and set all the terms and that's just not healthy!
I think the fact is, desire is scary, because we don't totally control it. And monogamy is a way of trying to control it that prioritizes the stability/safety of the relationship which I totally get! But there are totally ways of being monogamish that still prioritize the same. Like...it's really just sex. And it can even be something that happens together! And why would I hold back from new experiences just because there is programming that the right way is to keep everything just between two people? The fact is, there are totally things in being a little more open that intrigue me, it's just the fear gets in the way. Because the unknown is alarming! but if it becomes less unknown, it probably becomes less scary, or at least I can know for certain what I think, rather than having a knee jerk reaction control me.
This is a REALLY good point.
Re: 'it's really just sex' Other posters are correct, it's not necessarily always going to be or remain just sex. But that's ok too. In the end, trying to ensure everything is 'just sex' is just another method of control used to feel safe and secure. (Not that there's anything wrong with that between two consenting adults imo)