Speak to yourself!
Narrate yourself as you do housework, as you drive, etc. Speak your thoughts out loud.
When I'm alone, I'll converse with myself in Spanish. Depending on how good your imagination is (mine's not too shabby :P), things can get pretty exciting! Imagine a whole scenario, and explain it as if you were part of an audio drama. The more ...
There is no cut and dry answer as forgetting a language differs from person to person, but it is common to forget a language when it isn't use to a certain degree[source]. Interest and motivation also play a role. Instead of describing, here's a picture which shows the decline of memory over time.
Here's the typical "Forgetting Curve (scale might be off, ...
Even if you don't have the time to actively study a language, a little upkeep can go a long way.
It can be beneficial to recognize you're not studying actively for now, and decide not to study grammar, vocabulary or textbooks for a while. Instead, try to just use the language - just a little, but regularly. By recognizing that you're on a "break" from ...
To prevent yourself forgetting the language, you should basically use it on daily basis.
Here are few ideas how to do it:
use flash cards and keep them visible around your work place,
use some mnemonic techniques to repeat most troubled words,
print some language cheatsheet and place it where you can see it,
use some daily newsletters to read them on your ...
In my opinion, start reading books and watching videos (all in German of course).
Start with difficult stuff, stuff that only fluent German speakers could easily understand. If the material is too difficult to understand properly (that is at your discretion) then start going for material that less fluent speakers would understand. Continue until you reach a ...
There are many introductory books and grammars, but after that, there appears to be nothing that identifies itself as "advanced". So it seems you need to dive into the text, possibly annotated versions, or with a translation in parallel. Below are a few books that may be helpful:
Charles Rockwell Lanman: A Sanskrit Reader: Text and Vocabulary and Notes. ...
I was in a similar situation with Korean, and I found that when I started re-learning it, beginner material was too easy, but I had large holes in my knowledge in intermediate and advanced materials; however, it was hard to know what I didn't know. After randomly studying different things and feeling either bored and/or frustrated with them, I decided to ...
Use the language consistently and with passion!
Languages will often be forgotten if they are not used frequently. Slowly, piece by piece, the language will start to disappear as you no longer use that language. But, with continuous usage of the language, you can refresh your brain every day of your language and maintain fluency.
Like what Hatchet said, ...
From the National Center for Biotechnology Information:
... while simply overhearing a language during childhood could help adult learners speak it with a more native-like phonology, speaking a language regularly during childhood could help re-learners use it with more native-like grammar as well as phonology.
The study was done on fourteen-year-old ...
I believe that by "going 21st Century" and using the Internet, and then doing the following will help you quite a bit to re-learn much of the German you apparently believe that you have forgotten:
Obtain a copy of Barron's "German Grammar", which is a small, inexpensive, pocket-sized reference grammar intended for relearners, as it says ...
I'm thinking about the same problem with refreshing my Italian. My approach is to use Duolingo - you can quickly go through the things that you already know and focus on topics that are weaker. Plus, it's very addictive with its gamification element. I spent 20-30 minutes daily for the past 20 days and managed to go through most of the words a learned for 6 ...
Although you may not consciously remember them, given that you studied the words well before you went on holiday, your brain will still have stored them in the back of your mind. Therefore, when you try to relearn them now, it will be a much quicker process because you do unconsciously possess the definitions. (There's a psychological effect named for this, ...
It sounds like you lack opportunities to actively speak or write the language, even though you have opportunities to listen or read it.
One way to use the language is language correction websites like http://lang-8.com and italki. You write diary entries in your non-native language, and other users (native or fluent speakers) correct what you've written. In ...
Adding to the great answers by other members, I'd like to recommend (1) listening to Spanish language news through Podcast and (2) try to dictate (transcribe) what you hear when you have 10 to 20 minutes. You can listen while you are walking, exercising, taking a bus, etc. and no extra efforts are required.
Dictation is one of the most effective ways to ...
Since you speak German I think it would be already a good exercise for you if I continue by writting the rest in German to you but in order to avoid trouble I will just add a German translation for you.
So what I would do if I had forgotten about a language or if I lost confidence in speaking the language I once spoke before I would try to regain it by ...
A lot of apps, tools and practice methods fall short because the onus is always on you to open the app/textbook/flashcards and practice, every single day. Learning a language takes months, but retaining a language is a lifelong endeavor.
Flying to a Spanish city and immersing yourself in the language is considered the gold standard in retaining language ...
Try tuning in to a local radio station of the region whose language you have learned. You can also search out YouTube videos which present using the language.
Make sure to continue studying for at least half an hour per day too.
I know, without regular usage/speaking you can not remember the words and recall them. The best ways to be fluent in any language speakinig are:
Find the partner to speak daily.
Read more news, books.
Online discussion forums are the best way in your case.
Join free language bootcamps/workshops.
Books of your interest
Practice with a friend who speaks the language or is learning to speak it
To your self in mirror
Sing some songs