Always incorporate your vocabulary learning into four skills, that can make your learning more rewarding. 

When you are able to make use of vocabulary often in the sentences,  you would be ableto  retain these words more firmly with cohesion in the database of head. However, if you take learning vocabulary as a blunt retention of memory with no context association, you would be hardly able to accomplish the task well. Of worse is you will lose the benefit from the vocabulary learning by which you may enrich your speaking and writing. 

Forget is of human beings. Never mind it. 

Use spaced repetition and learn your vocabulary in context

Sometimes, I create a song to remember them. It sounds silly but it works