I don't use Skritter - I didn't realize you could use it for grammar practice but that's awesome! Anyway, it's very, very normal to continue to make mistakes in grammar and sentence structures when using them in everyday life, even after you understand them and have practiced them in a specialized learning situation. It happens because your brain hasn't fully internalized and automated them yet, and because you have to think about so many more things when you are having a real conversation in Chinese than you do when you are doing a drill in a structured situation. Just like in sports - you might learn a particular technique when your instructor teaches it and do it correctly in a drill, but being able to do it on a split second's notice in the middle of a game with everything going on takes a lot more practice. If you are living in China or in a situation where you can speak Chinese on a regular basis, the best thing is just to keep speaking, don't get discouraged, and remind yourself that you ARE learning. One thing that has worked well for me is to take note of the most common 2-3 grammar mistakes you make (don't try to focus on too many at one time). When you get home, think about the kind of situations you are usually in when you make these mistakes. Shopping? Arguing with friends about who gets to pick up the check? Talking about your significant other? Describing your day? Then think about how to use your target structure correctly in whatever that situation is. Replay the correct version of the conversation in your head a couple times. Try to get your mind in the habit of using the structure so that it will come out naturally the next time you're in that situation. But don't get discouraged - you will probably continue to make the same mistake a few more times before you start to get it right. I hate the intermediate stage of language learning for this exact reason.