If there is a Stack site this question is better suited for, please advise. I consider it relevant to interpersonal skills because it centers on the skill of negotiating/resolving a disagreement between two people (in a committed relationship).
Background
I am a 28 year old male college graduate with a full time job. I have a history of on-and-off drug use, but I am known among my friends as the most responsible and self-controlled user.
There were times my drug use was unhealthy, such as relying on amphetamine during undergrad to the point that it took a significant toll on my mental and physical health. There were also times drug use has benefitted me greatly, such as experiences with psychedelics giving me a greater sense of clarity and purpose during dark times.
I no longer use any form of cocaine because in a moment of weakness I became addicted to smoking crack cocaine for about two months. Freeing myself of that addiction was painful, but I did it. I was a cigarette smoker for almost 10 years, and have quit that addiction as well (just over a year nicotine-free). These last two years I smoke marijuana maybe once every other month, and use amphetamines once or twice a year. My urine is clean almost any given day, and I do not drink alcohol. I do not at this point rely on substances (other than a prescribed SSRI) to function in my life, or even for recreational enjoyment.
However, for the last several months I have been telling myself that when I get together with good friends I rarely see anymore this New Year's Eve, I will allow myself to "party" with them. I anticipate this to mean a night of recreational but not excessive amounts marijuana, alcohol, and a dose or two of methamphetamine or mdma. I feel like allowing myself this once-a-year indulgence helps me resist temptations throughout the year, and gives me something "special" to look forward to.
I find it reasonable and I do not expect it will disrupt my mental stability, other than a day or two of "hangover". I am aware of how to mitigate negative side effects and physiological consequences of various drugs, such as making sure to staying well-fed with amphetamines (to avoid muscle protein deterioration) or keeping body temperature from getting too high on mdma (and of course, hydration).
I am confident that I can use for one night and resist any continued use. I have done this many times in the past, resisting further use while still having a significant amounts left over. In fact, I am very passionate about the science and history of psychoactive substances and I keep a labeled collection of substances in vials for nostalgic purposes.
The Problem
I have been with my girlfriend for 16 months and we live together. She is not a drug user or a drinker. She has been tolerant of me occasionally smoking marijuana (though the first few times she was internally upset about it). We occasionally share a few drinks but we do not get drunk. I have casually mentioned to her my plans for New Year's Eve throughout the year, but she was never interested in discussing the issue, only stating she is against any "hard" drug use.
Over the last week, as NYE approaches, we have had several conversations covering many aspects of this issue. Each one is a bit more tense than the last, and we break them off before any resolution can be found because emotions start becoming too strong.
Question
What are some ways I can approach the interpersonal issue of negotiating a resolution/compromise with a significant other in regards to rare special-occaision drug use?