Duolingo doesn't work...
I finish my lessons , I get my points, but SOMEHOW I CAN'T STRENGTHTEN MY BARS AND THAT'S MAKING ME SO MAD!!!!!!!!!!!
If the strength of certain words is very low, you will need to strengthen the skill many times. If the weak word or words are not appearing in your practice sessions, it will not strengthen. At such a time, going through each of the lessons individually will help ensure you come across that word.
The more you peek, the more quickly your skills will weaken.
Also, keep in mind that the bars are a suggestion to help you strengthen your vocabulary. If you already feel solid with the vocabulary, ignore that features and move forward. Don't add undo frustration into the learning process :)