No, I’m not going to the office Christmas party this year, and yes, I’m feeling pretty happy about it. Thanks to the current cultural moment, in which we’re being more open about sexual assault than ever before, I feel safe being open this year about the fact that it’s because I was sexually assaulted at an office Christmas party. And though it’s a long time since I worked for that company – I left less than a year later – the thought of colleagues and alcohol and Christmas lights still makes my blood run cold.

After I was assaulted, and before #MeToo, I did still attend these parties: out of a sense of obligation, of concern that I would be judged to lack commitment or team spirit if I didn’t show my face. At the parties I would smile thinly, standing with my back to the wall, never dancing, never having more than one drink. At the parties I would feel afraid that if I told anyone the truth I would be judged: to be making it up, to be oversensitive, or simply to be ruining the fun.

That’s certainly how my then-colleagues regarded me that night, when the man who sat next to me in the office came up to me on the dancefloor, grabbed my breasts in each hand and dug with his fingers through the fabric of my dress and bra to twist my nipples.

I’m sure that some people reading this are thinking that maybe I shouldn’t have worn such a thin dress, and rest assured that’s what I thought, too, when I took the dress off upon getting home and threw it in the bottom of my wardrobe. I never touched it again until I moved out of the UK almost a year later, when I donated it to a charity shop. I loved that dress, had worn it on many happy occasions, but on that night, at that office Christmas party, apparently I should have worn a North Face parka over three burlap sacks and a layer of chainmail made with barbed wire if I didn’t want a colleague to sexually assault me.

At least that’s what many of my co-workers seemed to think. Some came over to see why I was so upset, after I pushed the man off me. “Oh,” they said, when I told them what had happened, “but it’s the office Christmas party.” “It’s not like you have a boyfriend,” said another, while a third helpfully pointed out that my attacker “is your friend”. And indeed, the office Christmas party has long been enshrined in our culture as a time when sexual assault is just part of the fun: six hours or so when women’s bodies are up for grabs in the name of the festive season.

From the little I know about trauma, I assume that the reason that I have never again been able to enjoy an office Christmas party is because I can’t bear to be around corporate carousers without feeling like I’m being dragged right back to that bar in east London, to those grasping hands, to the abject feelings of panic and disgust that I felt when I left and cried on the phone to a friend as I rode home in a black cab. Not to mention the nearly four months I spent afterwards in a protracted HR process until my assailant was at last fired, which meant that I had to continue to sit in a room with him every day for eight hours, and was ostracised by many of his friends in the company, who felt I had ruined the fun. (The #MeToo movement inspired me to Google my assailant, to see how his career is going. It’s going well, in case you’re wondering.)

Last night, a friend and I speculated about whether I could ever get over this: if exposure therapy might help. “I guess,” I said, “I could touch some tinsel in a safe environment.” “And the therapist could play Last Christmas while you do it, but only for 30 seconds.” Now that I don’t have to go to the party, I can almost laugh about it. The thing that man ruined for me for the rest of my life is just one night of the year. In that I’m much luckier than many.

• Jean Hannah Edelstein is a freelance journalist and author