Proper assertiveness statements, part of a broader class of assertive communication techniques, come in handy across situations, and along with the gentle limit-setting of a gracefully delivered no, they can help you draw clearer boundaries around your relationships. In the end, everyone benefits from this. You'll have a much easier time maintaining your integrity, self-esteem and sometimes safety, and your friends, partners, and dates have an easier time getting to know who you really are. Unfortunately, most people don't really know how to assert themselves. As others have noted, fledgling attempts to stand up for onself often conflate assertiveness with aggression, leave out important steps, or misuse assertiveness language altogether.
Three of the more egregious examples I've seen: "When you don't ask about my day, I feel like I'm living with a jerk;" "It feels like you're deliberately ignoring me, as usual"; and my favorite, "I'm sorry you felt hurt when I called you a lard ass". (OK, this last one's not really mishandled assertiveness. It's from a cartoon I read years ago–a hilarious lampooning of the faux-apology, but it's not too far from the kind of half-hearted attempts I've seen before.)
First, the Don'ts
1) Don't assume that sticking "I feel" at the beginning or end of a statement means you've stated your feelings or asserted yourself. Example: "I feel like you're a lousy listener when you just say uh-huh all the time."
2) Don't embed accusations: Example: "I feel like you're trying to start a fight."
3) Don't interpret behaviors (that is, don't tell people what their intention really is). Example: "I think you didn't call me last weekend because you don't care about me."
The ABC's of Assertiveness
Now for the Do's:
A) Use the word 'I' as often as possible: I'm hurt that you haven't asked me how my day was. I'm feeling a little shut down. Even better: I shut down when I'm not asked about my day. This last statement is an example of advanced assertiveness. It takes practice. People feel less defensive when they don't hear the word you. It keeps the focus on the behavior that needs to change, making it harder to feel attacked. This is a great deescalation technique. Strive for it, but don't get too stuck if you can't come up with a "you-less" statement. You shouldn't always have to work so hard to be heard. If you stick to describing your own feelings and the events you're reacting to, you've already done your part to keep things civil.
B) Describe the hurtful/problematic behavior: Four examples:1) I get scared when you raise your voice (or I get scared around raised voices); 2) I feel sad when you say nothing after I've shared a story (or I feel sad when there's no response to what I've said); 3) When I hear, 'you never do anything around here!' I feel demoralized (an example of simply repeating events or statements, the most efficient way to steer clear of potentially inflammatory interpretations like "you're just trying to bait me."; and 4) I get defensive when you ask me, "why did you do that!"
C) Make a request: Proper assertiveness always includes a request of some kind. This makes perfect sense when you keep in mind the ultimate goal of assertiveness: constructive change. Without a request, you're merely describing your feelings--and that's a good start, but if you want things to change, you'll probably need to provide a little guidance. Don't ever assume that someone knows what to say or do differently to make you feel better. More often than not, hurtful behaviors stem from lack of skill and knowledge, and you might need to teach people how you prefer to be treated. Some examples of full assertiveness statements, elaborating on the previous examples:
I get scared when there's yelling. I'd be more comfortable talking if you'd lower your voice.
I feel sad when there's no response to what I've said. I feel better when you ask me a question or just tell me what you think.
I feel defensive when you say, "Why did you do that?" If you're upset, I'd prefer it if you'd just say you're angry.
It hurts when I'm not asked how my day was. I feel closer to you when you ask me about my day.
This last example is another advanced technique. Rather than putting the emphasis on what someone hasn't done, the speaker asks for more of what they have (with the face-saving implication that sometimes the listener even gets it right). You can learn more about the technique here.
Putting the do's together, you now have a simple strategy for maintaining the assertiveness structure across all situations:
I feel A (feeling) when you do B (action). I'd feel better if C (request).
Example: I'm hurt that you're walking away from me in the middle of my sentence. I'd feel better if you stayed until I finish.
(or, to create a you-less statement):
I feel A when B happens. I'd feel better if C.
Example: I feel hurt when people walk away when I'm talking. I'd feel better if you stayed until I finish.
There you have it: the ABC's of assertiveness. Don't worry if it feels a little clumsy at first, or you find yourself speaking more slowly. Slow is good. Having to think about what you're about to say can help deescalate potential conflicts. You'll find if you keep this simple structure in mind, the technique gets easier and easier. Just keep practicing. Soon you'll be rattling off assertiveness statements as easily as the alphabet.