This might sound obvious, but if you don’t have a good reason to learn a language, you are less likely to stay motivated over the long-run. Wanting to impress English-speakers with your French is not a very good reason; wanting to get to know a French person in his or her own language is another matter entirely. No matter your reason, once you’ve decided on a language, it’s crucial to commit:
“OK, I want to learn this and I’m therefore going to do as much as I can in this language, with this language and for this language.”