Ok a quick history about myself. I've spent the last year living and working in China as an English Teacher. As well as teaching English I had been (and still am) learning Mandarin. Through both teaching and learning a language I started to notice a few factors in success. One of them I want to talk about today is retention through repetition.
For anyone new to English, retention simply means "the ability to hold onto something". For example, if we have a one hour class and I teach you 100 new words, that's great but... how many of those words will you retain? Probably not many right? However if I teach you between 4-6 words/phrases, it's a lot less but you are more likely to "retain" / remember them next time.
We tend to retain knowledge better the more we repeat things. That's why at the beginning of a class a teacher may ask you about the previous class and what we learned there (to refresh your memory), this isn't to kill a few minutes of the lesson but a quick way to improve your retention of what you've learned.
In fact the more we repeat something the better it sticks. So when I'm learning Mandarin and I learn a new phrase, for example 善良 (ShanLiang) which means "Kind" then I will use it in most sentences with Mandarin-speaking people. Even if it sounds ridiculous. I will keep using it in as many ways as I can until I no longer find it difficult to remember. At that point it's "stuck" in my brain.
Now just because it's retained a bit better, doesn't mean I can't forget it. So it's important that I still try to use it. I may not have to use it as much to still keep it "locked" in my brain, but every once in a while is fine.
So now try it with your language. Think of the last few words / phrases you learned and try applying them in as many different ways possible when practicing your english and soon enough you may just find yourself remembering things just a little bit better.