When you were in school, in all of your English classes, grammar was heavily enforced. You would lose points if you used the wrong tense, punctuation, and other such small grammatical errors, and I was never very good at following directions. I could write grammatically very well, but I didn't like to, and I've come to realize in the years since I left school that small grammatical errors aren't as important as your high school English teacher would lead you to believe.
Now, don't take that as an excuse to throw those rules to the wind and write sentences in a jumbled, convoluted manner. That's not what I mean. What I mean is that when it comes to grammar, how particular you are depends on two things: your audience and the type of writing you're doing. Fiction writing, whether in first or third person, has a tendency to ignore grammar at times in favor of a certain style, and the tendency works quite well for some authors. An academic paper, however, would not allow someone the same leniency in grammatical errors as, say, a blog post. Each type of writing you might do has different leniency due to how formal or informal it is meant to be.
This is largely because for more casual writing, such as blogs, the writer wants to connect to the reader on a more intimate basis, and people often relate better to others who have their own little quirks than those who have perfect writing. For example, my odd grammatical quirk is putting a 'u' in certain words, such as 'favourite' and 'colour'. In American English, this is incorrect, but without fail I do this in almost everything I write. Part of the reason for this is because my Grandmother is very British and I've picked it up a bit. Often times, genre of writing and audience are tied together. Not many children are going to read college papers, so you needn't worry about making it accessible to them.
However, if your writing is targeting teenagers, then you don't need to worry about grammar as much as you would if your target audience was Professors. The more strictly you stick to grammar, the more educated you are assuming your audience is. While not entirely true in practice, that tends to be the thought. So if you're writing a blog post designed to attract teenagers, you can ignore grammar and use 'OMG' and 'LOL' and other internet short hand without it being too odd, but it would be inappropriate in a resume (something my friend, who is in HR, has told me has happened before).
Which brings me to the biggest point of all. Grammar is not as important as how understandable you are. Your grammar can be immaculate, but if you are targeting the wrong crowd with your writing and they don't understand you, there is little point. Grammar is, after all, a set of rules to make people more easily understood.
Whether you bend the rules or not, that's the most important part of grammar: how well are you understood? Can the reader understand what you are trying to get across to them?