I used to send emotional texts, by emotional, I mean it was me spewing vitriol, usually at my bf.
I bought a "*****ing out bf" journal... So whenever I want to send emotional walls of texts, I write it out in the journal instead, there's no "send" button to impulsively click on.
I sit on it, edit and rewrite for a few days, and if by the end of day 5 I actually had a valid message in there, all the editing and proof reading has been done, so I type it out and we discuss it calmly.
I should mention, that after doing this for a few months, maybe a yearish?
I very rarely have a strong compulsion to write and send these types of communication. Being able to sit with the thoughts and feelings have now become second nature, and second is better than not in my nature at all.
Ps. DBT does take a lot of practice, so go easy on yourself, I'm doing my second round this year.