Just practicing really. Mnemonics are also helpful but they can only go so far. Forgetting and rediscovering things is a normal part of learning, not something you should be scared of
Learn grammar and sentences. They're a great way to learn the meanings of words in specific contexts. And like @GD_V said above here, forgetting words is part of the process, and sometimes the words you forget are the ones that you remember the easiest. Keep up the work!
みみ, you absolutely do need context to remember, the more context the better, but renshuu can’t provide that context for you. You have to find it yourself.
TBH, there's only a few examples I can think of which have some interesting context within them. In some other cases, like kanji for example, shift words based on their use and sometimes because of grammatical rules. These things offer good clues.
But as far as knowing them? Pretty much the same as any language. Match the word with an English equivalent. That's your word. With that, you can roughly translate words when they're put together with other words. Again, in some cases, grammar terms help a lot in showing the word's purpose. Thankfully, the grammar is fairly consistent in telling you what the word is doing. You just have to figure the meaning of the word. Take your best guess if you don't know. Or look it up. After a while of repeated exposure, you should do better at being familiar with it.
If you're only using renshuu, practice sentences A LOT.
It also helps to make your own sentences, at least in your head, while quizzing.
I personally only add to my schedule the words I have seen in any of the videos or texts (I know It's not that simple if youre learning for a test or something, but in terms of the language itself, it kinda works?)
