Communication skills are vital, whether you're a freelancer or an employee. Unless you are so gifted that clients are queueing up to get a chance to beg you to work for them, or you have guaranteed tenure on a job for life, you will need to sell your skills to clients or employers, and to do that you need to have good communication. As Guido says, you'll be able to judge whether your communication skills are holding you back at the moment, but you also need to look to the future.
Start with the basics. That post you just made, for example – on the basis of that, I wouldn't even look at hiring you to do what I would call "mental" work ("physical" work might be different). Ten missing capital letters, and more besides. Now maybe when you're writing for work, you put more effort in, you go back and proofread it, you don't send out material with basic spelling and punctuation mistakes. But why allow yourself to get into bad habits? Don't think "Oh, it's just a forum post, it doesn't matter", make a point of getting your writing right every time. Sure, there's no need to spend hours going over every little thing with a fine-tooth comb, but just put in a bit of effort to get the basics right, and it will become instinctive. If you're doing technical work, you need to be able to present yourself as intelligent and educated to win the confidence of people who don't know how good you are at your job.