I need to write an apology by tomorrow

I need to apologize to a Japanese girl I like. We were getting along great. She was very flirty and touchy towards me, as I was to her, but I guess I misread a lot of that. I made a move and I think I made her uncomfortable, which is the last thing I wanted to do. She might like me, I'm honestly still unsure. I might have just surprised her a little bit. My Japanese is awful so it's hard to communicate.

Anyways, I just want to say this quick message Japanese without all the translation errors. Also in Japanese characters please.

"I'm sorry about Monday. I was not thinking clearly. I thought that was what you wanted. :("

"I'm sorry about Monday. I was not thinking clearly. I thought that was what you wanted."

Having been married for 10+ years in an international marriage, I have learned to apologize in my language and to keep it simple. I can see how the I thought that was what you wanted part could set you up for a very long discussion. I would just write "I'm sorry about last Monday, I don't know what came over me" or, if you want to do it in Japanese, a simple "Gomennasai" and some other humble words will hopefully do the trick.

My advice is "Don't apologize.. Just forget her.".

Sending an apology message to her will NOT solve your problem.
Most Japanese girls don't like a person making excuses (whatever you write in your message and even if you behave honestly, the result will be the same).

日本の女性は、しつこい人や言い訳する人が嫌いなんです

The only way to solve your problem is to let her alone and to forget her. In Japan, leaving her alone sometimes means
kindness and honesty, because she can choose
another way to live.

I agree with Hoshisato, and I strongly disagree with dosanko100. dosanko100, the original poster is not being persistent or making excuses. He behaved in a way she did not like, so he is trying to make an honest apology. As Hoshisato suggested, stockwell, just apologize and see what she says.

First off, I am assuming you didn't try to force yourself on her and didn't commit any crime.

That said...

If you're old enough to put the moves on someone, you're old enough to talk about the issue without a note.

While you might want to apologize for making her uncomfortable, apologizing through a letter is like sulking into a hole.

Is that even what she wants?

If you want to apologize, by her flowers and dinner and promise you'll take it a little slower next time.

Miscommunication happens in all relationships and those in an international relationship where there is a language barrier will occur 10 fold.

You're going to make mistakes and you're going to embarrass yourself but the natural language between men and women is pretty much the same in any language.

Otherwise, you could be running away from a potential relationship.

いいですか
そうゆうときどうしても謝りたいなら、
自分の非があったかもしれないことをわびて
相手にどうすればいいのか、すべて決めてもらうことです。相手に言い訳したり、自分を正当化すると
いい結果になりません。これは文化の違いです。基本的に相手を困らせちゃいません。相手に決めさせることです。

There's definitely some valid culturally-based differences of opinion but dosanko100's response is very typically "Japanese".

(Although, if you're going to write such a pointed response, why not write in English considering the OP doesn't understand Japanese and no online translator is going to get that right).

The idea of apologize and then leave everything up to her? That kind aggressive-passive thinking is, IMO, boring, irresponsible, and not very attractive when displayed by us men.

By the way, in response to your original question of how to say...

"この間はすみませんでした。同じ気持ちでいると勘違いして、何も考えずに行動してしまった。ごめんなさい。"

Thanks everyone. I appreciate this a lot. After reading all the posts, I think I'm going to go with the short and simple answer...

"この間はすみませんでした。同じ気持ちでいると勘違いして、何も考えずに行動してしまった。ごめんなさい。"

Thank you to whoever wrote that. I would say it to her face, but knowing me, I would butcher it beyond recognition. I'm going to write it on a piece of paper and show it to her. I'm meeting with her tonight in maybe 6 hours. I will report back my results (success or disaster). Wish me luck.

Wow (guest), you are a god among men. Did you translate it exactly?

"この間はすみませんでした。同じ気持ちでいると勘違いして、何も考えずに行動してしまった。ごめんなさい。"

The second I showed her it she smiled and tried to cuddle with me. That couldn't have worked out better. Thank you so much. I mean it.

It had a slight nuance that I hoped would get you that type of response.

It seemed like a waste to apologize and then run away and hide.

Glad things worked out for you.

And don't forget, it's OKAY to be an alpha male. "Aggressive yet respectful" does well (in love and business) in this age of passive/passive gender neutral men...

By showing her a piece of paper with writing that is definitely beyond your knowledge of Japanese, she's going to know you're using someone else for help. I don't know if that's something she'd like to know-that you're involving someone else in something that may be very personal to her. Just my two cents....