Text messaged failed to send

Hi guys,

I tried to send my friend a message a month ago, but it never went through (as pictured below).

I need to text this friend again, but I was wondering if when I do this, will my old text which didn't send through earlier also send through with the new, unrelated message I need to send?

If it does, how do I stop it from doing this!? The old message that didn't send a month ago is now no longer relevant and it would be extremely awkward if it sent through when I tried to contact this person again.

Does anyone have a sure-fire way to make sure it will not try to re-send?

Thanks in advance.

(iPhone 6s)