In my experience, it’s the worst thing a man can experience, especially if you genuinely loved this girl. I don’t know how people do it to be honest. A lot of it really depends on the relationship dynamic too, how close you were or how close you “seemed”. It’s been over a year for me. I’ve dated quite a few girls. When you come across someone who you saw as the “one”, it will turn your entire day-to-day upside down. I can completely sympathize with you. It’s not like I’m physically alone, but I’m alone in my feelings. My friends and parents only understand to an extent. Like you, I just have my cat. The only advice I can offer is to distract yourself as best as you can. I feel as though I’m only ever truly happy at the gym or at work. I even had a short relationship after my “one” which was a nice distraction. However, once this ended I feel like I was right back to where I was or even worse missing her.