Writing: Professional vs. Personal

On Grammar- Can you distinguish the difference between writing professionally and writing personally? The article linked to this post is a quick read and a great reminder when it comes to basic writing skills. If you can transition from a casual, informal text to a professional, formal business letter with ease, I applaud your writing skills.
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Let's look at two quick examples:

Is the following sign off appropriate to include in an email to your boss?

Thx! C U L8R! 

Or.....

Am I being overzealous if I include the following in a text to a close friend?

Thanks! See you later.

The first sign off is very informal and the second sign off, to some, may seem too formal. I think the best rule to follow is to make sure all of your professional emails, texts, memos and other forms of communication remain formal. When it come to informality, it is up to the individual. If your friends and family are content with the way you communicate, so be it.
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I will admit that I use proper grammar in all of my writing, including texts. However, I am making the attempt to loosen up a bit when I read informal messages/posts on FB, IM, IG, G+, etc. Grammar and punctuation errors make my teeth grind, but informal text and slang are a whole new ball of wax. I'll never be okay with 'cuz' and 'cause,' unless you are writing about saving the whales, but I do see the reasoning behind LOL and YOLO.
Language and expression are constantly changing. My 90 year old grandmother grew up using the word 'gay' to describe joy and happiness; we now use that term interchangeably when describing sexuality. Will we go back to using the word 'gay' to describe someone who is full of joy or will that definition become lost with future generations? Will it become a section in an Etymology book, explored by weirdos like me who are fascinated by the origin of words and phrases? I do believe it is safe to say that the English language is both torturous and tricky.
When it comes to grammar, there are endless rules and exceptions. A single word can be used as a noun, verb, adjective, and adverb:

The painted painter paints paintings.

This example is an obvious stretch, but it shows the complexity that lies within language acquisition as well as learning a new language. Teaching the difference between

are, our, and hour

is a frustration I have personally witnessed as an educator.  As long as we progress and move forward when it comes to language and writing, future generations of English speakers will be just fine. If we remember the importance of using audience appropriate language, we will have done our job preserving this chaotic, yet beautiful concoction of words we claim.
In the spirit of our ever changing language, I may even use YOLO in a text one day. I mean, you only live once, right?