It is often said that 'men in their first sexual relationship cannot forget' is a fact. In short, no matter what happens, the "first time" is always imprinted in people's memories. For example, the first time you smoke or drink alcohol, your memory will update. The situation of your first overseas trip should be clearer than the second time. This is because the 'first time' of anything is a door leaf in memory, making it the easiest to recall.
So 'not forgetting the first man' is not because we cannot forget the things we dedicate to ourselves, nor because we have deep memories, emotions, or the influence of our first experiences on our lives. If you really like the first object, you may not be able to forget it, but usually it's just because the so-called 'first' is still in your memory. I think the correct statement should be not to forget the first and last male characters in the memory system, initially because they were unforgettable on the first night, and finally because they were on the last page, they were deeply impressed. Finally, for older women, and for women who played humans with their last teacher a few years ago, perhaps not in the past month, last time with that person. From the original meaning, 'unforgettable man' should be a man who is in love with Zhang Gao. The second or third, should be left deep in memory.