Stay Positive and Understanding
Many times in your career, you'll receive an email or have a meeting that isn't exactly what you expected. And you'll be slightly annoyed, maybe even angry. My advice is don't be. Your feelings might be valid, but take time to remain professional and positive. If you need to step away from the conversation to avoid an emotional response, do it. Check and make sure you're fed and hydrated- low blood sugar can sometimes get us up an arms simply because we read something wrong. Run the situation by a friend to get feedback on what to do. Your attitude is important, and a lot of time clients pick people who are the easiest and most pleasant to work with- not the most talented or best value.
There's also going to be situations where you have to patiently walk your client through the process. Lots of hand holding. This might involve reassuring them you can deliver this, explaining how the typical process works, what is and is not considered scope. Take this time to slow down and work with people. We all get anxious and confused, and life runs so much better when every remains calm and patient. If you find yourself working with someone who doesn't keep a calm head, you're probably working with someone who is just going to cause unnecessary drama and stress down the road, and you'd be better off moving on from the project. The same could be said about you, so no matter what, remain calm, professional, and firmly stand up for yourself without coming across like an ass.
TL;DR: Be nice and professional to people. No one has time for rudeness.
Context: So a little bit ago, I went full time freelance. It's been a ride full of lessons learned. On my instagram, I asked people for their diehard rules of the trade, and I compiled a list that should help people run their businesses a little more smoothly. If you have some design rules you live by, feel free to comment or message me on Instagram. https://www.instagram.com/darumacreative/