English is such a big language - so many words and rules and exceptions to those rules - that you have to develop a "good ear" to prevail over its obstacles and benefit from its possibilities.
A lot of native speakers aren't familiar with many of the grammar rules that govern their mother tongue. But they can hear what "sounds" right or wrong.
Developing a good ear in English doesn't have to be painful. A lot of it can happen through a type of linguistic osmosis. Spend enough time with the language and you will begin to automatically absorb what native speakers know without even thinking about it.
What do I mean by "spend enough time"? Ideally, this would be some type of interaction with the language on a daily basis. At the very least, I think these interactions have to occur several times a week.
How you decide to interact is completely up to you. Do something fun or interesting or relative to your profession. Do something you enjoy and it will be easier for you to come back to it more often.
Our classes together can only do so much for you. Real progress will come from what you do OUTSIDE of class. Watch TV, movies, Youtube, etc. Pay attention to the language as you watch and avoid reading the subtitles as much as possible.
Read the internet in English. Listen to the radio or a favorite podcast (1, 2, 3). Check out an exciting book from your local library. What about an audio book on CD/tape in the car as you drive around? Rana library has a selection in English.
Try to make dinner tonight following a new recipe in English. I like http://allrecipes.com but there are a lot of places to find good recipes. Just google the ingredients you have to work with and practice following directions in English. I guess you and your dinner guests will know if you have been successful.
Stay tuned to this blog for more suggestions to help you develop that "good ear" in English. In the meantime, here are some of my other personal web favorites:
Given the season, how about taking 5 minutes right now and reading about "Halloween" from Wikipedia?
If not Holloween, then how about this NPR interview for a new collection of stories based on fairy tales? You can listen to the interview and read the transcript at the same time to work on pronunciation.
Looking for something more entertaining? How about this short story from Michigan writer David Means?
Or this article on the father of modern advertising?