Breaking up with someone should generally be done in person. Breaking up by text or email is harsh and cruel. Obviously there are exceptions to that comment, but if you have spent time with another person in an intimate relationship, the least you can do is break up with them in-person, even though it is hard for you.
Expressing anger in person is usually more conducive to resolving the matter in dispute than telling someone off in writing. Children's custody battles become so ugly so quickly when both parties lawyer up and start writing affidavits about what a lousy parent the other person was and is. Mediation of parenting issues is typically far more productive at creating a workable plan and less destructive for the family.
Many people use written communications to be ruder and harsher than they would be in person. My goal is to ensure that any of my communications, whether written or in person, convey a consistent tone and message. We'll see how it goes...