"You're always late."
"You never have anything nice to say about anybody."
"Are you ever organized?"
These statements are absolutes. Statements like these ought to ALWAYS be avoided in conflict situations. The previous statement was one of the few appropriate times you could use words like "always" and "never". The appropriate times are very few. Therefore, they should be avoided as often as possible. Here's why: most of us are rarely always doing anything or never doing something. To make such a claim is likely false, and people hate to be lied to or lied on. To make a blanket statement about someone's behavior--especially if that statement is largely negative--is to create conflict or add to it. Think about it: you rarely do anything all the time. There are few things we never do, but they aren't usually perceived as a criticism. For instance: "I never rob old people." That's obviously a plus so it's okay to make that absolute statement (if it's true). However, if an absolute statement is laced with criticism like "You never help me with the housework!" then you're likely to get some push back if that statement isn't entirely true and is accusing.
When engaged in a disagreement, stay away from making absolute statements or using words that rob a person of their contributions--no matter how minimal--to a particular situation. The other person may not help with housework as much as you'd like, but they do offer some help on occasion. An individual might live and work in clutter the bulk of the time, but there are a few times when you've seen their environment in order. Moreover, these types of words also have an accusing quality. It's a judgment upon on another person, and you've just opened the door to get something you've done thrown right back in your face. Then the tit-for-tat happens, and the conversation devolves into an ugly confrontation.
Changing the way you approach a person's lack in life should grab positive attention from them so that you can encourage them to listen to you better. For example, rather than accuse your coworker of "never picking up the slack on the team", you can say: "I appreciate it when you help out. I'd like to see you do more of that. It helps us get more done faster. We need you, and you do a great job." We must practice caution and care when engaging in conflict with others. Using a simple rule like this one can help.