I recommend using a Spaced Repetition Software (SRS) program to memorize phrases, vocabulary and Kanji. I use Anki that is a free source app and you can gather the card decks also for free in their community website. Had become really useful for me I can memorize much better than writing down because is an effective spaced learning. I just use what I learned writing everyday some sentences from my own to reinforce the SRS system learning and to make it practical. I hope this information is useful for you, had worked on me :) Cheers!

I think you can try some exercise memory game or buy some exercise the software of the memory.Hope these suggestions are helpful to you .