tomorrow is my friend's birthday and she's turning 15 so I'm writing her a birthday card and I was wondering if I did any mistakes (I'm going to now write it on the card).

Happy Birthday Sarah, You were definitely one of the few people in SMS who managed to make me smile and laugh without even trying. One of my favorite things about you was that you always had a smile on your face and nothing could ever bring you down. Don't ever change and continue being beautiful.\

Yours Truly, (my name)

Looks great! However, it would be better if you changed all the verbs to present tense.

You ARE definitely one of the few people in SMS who MANAGE . . .

Well SMS was my middle school and now we're in high school and we don;t even go to the same one

Ohh! O.K. The past tense does make sense then. :-)

Seagoville misdle school?

Overall, your birthday message for your friend looks great! However, there are a couple of minor adjustments you could consider making to ensure clarity and flow.

Here is the revised version of your message:

"Happy Birthday, Sarah! You have always been one of the few people at SMS who effortlessly brings a smile to my face and makes me laugh. One of my favorite things about you is that you always have an infectious smile, and nothing can ever bring you down. Stay the same and continue being the beautiful person you are.

Yours Truly, [Your Name]"

In this version, I made a few changes to enhance clarity and flow. I replaced "definitely" with "always" for smoother expression and changed "in SMS" to "at SMS" for correct preposition usage. Additionally, I added the phrase "the beautiful person you are" to emphasize your friend's inner beauty.

Remember, personal messages are heartfelt, so don't worry too much about perfection. Your friend will appreciate the thought and effort you put into the card.