I can't trust something that seems to be happy that I haven't visited in a long time.

Unhappiness is also impermanent, so not all bad things will continue.
Of course, meeting someone is also called the beginning of parting ways.
That's why there is also the term once-in-a-lifetime meeting.
Anyway, you and your girlfriend, are all human beings who are the cutest.
That's why the Buddha explained that we must avoid hurting others.
Please be polite in close relationships so as not to hurt the other person, but please cherish every moment of time between the two of you.
By the way, before becoming a monk, when she was a prince of the Shakya tribe, she married Princess Yasodara.
So, according to legend, the Buddha and the princess met long ago in their previous lives.
In Buddhist wedding manners, we perform a custom (offering flowers) derived from that story.
So, if your current relationship is wonderful, even if it's temporary, you may meet that girlfriend again in some form someday in the future.
So why don't you think that your relationship won't be wasted since you broke up, and that you cherish every moment?

　There seems to be a Chinese proverb that says, “Humans walk while facing backwards.” In other words, I'm always walking while referring to the past and watching “the old days were like that, like this.”
This story says, “Tomorrow is a new step anyway, so let's at least walk with a fresh feeling,” but it's difficult. If you were to fumble with everything, you could only walk solo.
but. As Mr. Kiyoshi Gan says, various acts are impermanent. Your “present” view of life, which you have learned from the past, is not immutable. “Oh, I want to spend the rest of my life with this kid!” It's OK for the moment to come when you think about it.
The words fleeting or eternity also come up, but if you're looking for “forever is fine,” then your life will end in an instant. Do you want eternity? That is a kind of arrogance. That's because you're not eternal.
Rather, what doesn't change is the information side. Your post probably won't go away unless you edit it yourself. It doesn't change. That's why I don't want you to be caught up in what you are “now” thinking like this. I'm the cutest. Therefore, humans tend to try to maintain consistency with their “what they said = the past.”
Of course, “you have to make sure you don't hurt” others is correct. However, although this is a subtle point, it's not “game over if you hurt it.” “It can also hurt. At that time, notice it as soon as possible and recover,” I think (otherwise you won't be able to learn). It's the difference between being able to say “sorry” or avoiding it beforehand and trying not to say it. Your “don't take it for granted” is linked here. Even now, it's possible that you're already hurting her in something.
One of hasunoha's recent “answer” trends is “did you say that to that person?” There is. Why don't you expose your current thoughts, “But I'm attracted to them.” Like a young literary man. The image of “having contradictions” as it is. Being honest is very important. Maybe she'll tell you, “I'm not that old girlfriend.” What about those who have contradictions between ordinary people. If we share that premise, I wonder if we can go.

Certainly, it may be a fleeting happiness. But it's true that I'm happy right now.
You must be aware of that sense of happiness and security. My heart is responding honestly.
However, they try to deny it with their head, and they hold it back because they don't want to get hurt.
No one knows the future. It also makes me anxious when I think about it.
However, it is a fact that unmistakably exists now.
In fact, cherishing the girlfriend right in front of you and creating a relationship where we can cherish each other will probably lead to happiness in the future.

everything is impermanent, so someday it will come to an end, oh wow
Things are impermanent, so it's not like they'll break up someday.
Everything is impermanent, so you've forgotten about your previous girlfriend with Kerorin and are having a great time with your current girlfriend.
Everything is impermanent, so when you're looking at these characters now, it's refreshing because you haven't met her until a while ago, and there isn't any left in this body or mind.
Since everything is impermanent, the first title and first line have already been played and said.
Since everything is impermanent, they are always saved.
Since everything is impermanent, there are no leftovers from what was up until now, and now they are blooming at their best.
Most of the solid imperfections described in Japanese language textbooks and Buddhist books are negative thoughts, and they are far from the Buddha's teachings.
True impermanence is the teaching of salvation.
Since everything is impermanent, everything in front of you right now is brand new.
Everything is impermanent, so even if you go to the same store as her, you can have a brand new date there.
There is no “see you again.”
There is no such thing as “it's over and it's empty.”
It's “always over and refreshed.”
Since various acts are impermanent, “bad humans” have already finished bad humans, and now they are blooming anew. Our human mind is impermanent, so it's always fresh, and fresh water is always flowing like a flush toilet. (After getting excited up to this point, is it the bathroom at the end?)