Welcome to Android Central!
Copy and paste the text into a new message:
1) open the messaging app
2) open the conversation in which you typed the message
3) press and hold the bubble containing the text you want to resend, which should result in a pop-up menu with a "copy" option
4) paste it and try sending again
If you need additional help or have more questions or details to share, please join the site so you can reply in this thread. See
this link for instructions on how to join Android Central.