Language learning is not exactly one skill, but rather a group of closely related skills: reading, writing, speaking, listening…
You get better at one by actually using it, and as a side effect, it makes easier to improve the others. But you never acquire the other skills without training them specifically.
In my case, I like anime, so I watched a lot of it in Japanese, and now it just feels natural. The problem is, I neglected writing. I could start chatting with strangers on the internet, but since I don’t even do that in English, I’m definitely not going to do it in Japanese.
I need a smaller step, something that fits better with my current habits. So here is the plan: for every anime episode I watch, I will make a tweet in Japanese. Maybe a little joke or an observation.
And if it gets me writing, then it will work with anyone else too. You can choose a different hobby and a different target language. Next Year I will show the results.