learning a foreign is really a tough process indeed.i can totally understand it when you said you feel like a child and are temped to give up halfway every now and then. i have studied english for several years , but still i am not articulate when talking with people from english speaking countries,i often stammer while talking because my head is blocked and words and phrases i've learnt just slip my mind.
I agree with you that children are best language learners, not only because they get no complaint thought to express, but also they would not feel ashamed of their flaws as we adults do!