<human>: I've been in a relationship with, let's say, Alex for almost a year after having known them for most of my life. Shortly after we got together, Alex told me that they had never really identified as a girl and wanted to be referred to using gender neutral pronouns and experiment with androgynous styles, presentation, etc. This didn't bother me at all. I think I was pretty supportive (minus a few mistakes which we talked over.)

As time passed, they started leaning toward top surgery (chest reconstruction, to get a more masculine chest) and taking testosterone. I had said early on that I didn't think the relationship could continue if they made physical changes, but Alex wasn't interested in doing so. Now they are.

I had tried to convince myself that I'd be able to give it a shot even if they did, but during a recent discussion I realized that I was lying to myself and couldn't be in a physical relationship with someone with a masculinized body. There's been a lot of crying on both sides since, and we're tentatively planning to stay together as long as we can.

This is the best romantic relationship either of us has ever had, and the best interpersonal relationship of any sort that Alex has ever had. I don't want to lose it entirely, but we're both devastated.

Earlier today, Alex said that I broke their heart. That really upset me. I agree that their decision is the right decision if it's what it takes for them to be comfortable in their own skin, but they're still the one with agency in this situation. I'm not sure if I should talk about how I felt when I heard that or let it go. I'm really not sure what to say or do overall right now.

Can you provide a brief rundown of the text in within 3 sentences?
<bot>: SO is changing their body in a way that ends our relationship. How can I be supportive without destroying myself as they go through this change?