Handling negative client feedback
Don't take it personally
If you define your project goals, give a clear revision policy and communicate throughout the project you're going a long way to making sure you have a satisfied client; but if a negative comment does come your way try not to take it personally.
They're very unlikely to be making a personal dig at you or your work and although it can be easy to feel deflated after putting your heart and soul into your work, this is your chance to learn from any mistakes and (believe it or not) build your confidence in your work.
Focus on the solution
When you receive negative feedback it's very difficult not to focus on...the negatives. By focusing on the solution, not only will you show your client you are proactive and dealing with any issues head on but you are also building more confidence in yourself and tools to eliminate this happening on your next project or with your next client.
Learn from the experience
You may feel you didn't do anything wrong and you just had a difficult client so there is nothing you could have done about it. This could be true but when you look at the experience as a whole you're bound to be able to see some things you could have done to help the project go more smoothly.
Whether it's communicating your expectations more clearly, keeping a written record of agreements in the messaging system or even taking on the wrong type of project for you there are always things to take away and build on.
Project messaging screen example, with personal details blacked-out