It is stressful to be on the spot about something so important to you, so it is natural for it to be draining. I suspect what people saying it isn't difficult mean is that you don't get the third degree. You still worry about what you say & your tone & your body language, etc. Very tiring. Try not to analyze every detail, as it will only stress you more. That is done. Time to focus on now.
And it sounds like things are going well w/ STBX. I'm so grateful that my W & I are so flexible and work well together on this stuff and keep the kids needs central. Making it less stressful is also one of the ways that allows approaches to be made. Hey, it's not unpleasant to be around S in this most difficult time in our R. Not enough by itself, but it at least offers hope that you can feel your way back into a friendship, and then see how it goes from there.
That the process my DB coach says is the path we are hoping for. Getting comfortable working together cooperatively, and then unconsciously falling into a bit of pleasant small talk, and then hitting on something that was of mutual interest or that was part of what drew you together in the first place. We can't help who we fall in love with. We can fight it. We can have issues that get in the way of allowing ourselves to open up to it, or make it too hard to turn the feelings into healthy loving actions. But having those moments you did w/ STBX are where that might happen. I hope it does for you if you still want it if & when it happens.
Me: 50 W:43 S6, S3 M: 12 yrs. T: 17 M is bad & Not happy Bomb Mar '14 S 5 Feb '15 D Bomb 13 Apr '15 (but "no hurry") DB Coach May '15 Wants proceed on D Aug '15 Starting 1-on-1 negotiations Sept '15