Losing a partner is, without a doubt, the most destructive thing that can happen to me. I don't handle it well at all. It's happened on numerous occasions (not to death, but to breakup/divorce) and the last two times I discovered the wonders of what the doctors called "situational depression" or something like that. When I'm single, I'm depressed, and when I'm not single, I'm fine. However, the last breakup has put me to a point that I no longer have a real interest in finding someone new because of how poorly I handle breakups, and let's face it, I'm clearly not very good at keeping a relationship going for life. With this in mind I've kind of just put myself off of relationships entirely, for better or for worse. I won't be as happy but I won't get to the point of being suicidal again once the next one ends and that's what I've settled for in life at the moment.
But hey, thanks to my friends, family, therapy and doctors, I'm still here. Again, for better or for worse.
Bri, FWIW, I don't suggest going down my road, it's not a fun one! I would strongly suggest getting therapy if you are finding this is impacting your day to day life. You and your partner both deserve to understand any underlying reasons for why this is troubling you, so you can both help make your life a better one.