Never give up when the going gets tough.
If you can't fly, then run. If you can't run, then walk. If you can't walk then crawl. But whatever you do KEEP MOVING FORWARD - Martin Luther King Jr. Remember there are always 3 people backing you up. Think of them as Me Myself and I. One language sets you in a corridor for life. Two languages open every door along the way.
For me,studying languages doesn't come from "motivation" or something, I really do it for fun and for the usefullness of that in the future. If it's not fun for you,if you're not really passionate about it,if polyglotysm isn't in your blood- then it doesn't matter how much willpower you have,you're going to get demotivated over time. You need to find a language you LOVE learning and not just one that "your friends told you it's useful", "chicks love that so I should probably learn that language" etc. It should be something you love doing. If you find yourself over time strugling and forcing yourself to do it- then you won't really get far..