I also have found the combination of personal environmental impact reduction combined with a sort of "Pale Blue Dot" nihilism helpful in my everyday life.
I'm genuinely interested in how you find comfort in nihilism (I currently don't, but I'm not against the thought). Have you genuinely changed your attitude towards the universe, are you just ignoring your sad thoughts, …?
That nothing matters at all in a grand scale frees you from the burden of having to matter. No legacy, no contribution, will ever be capable of cementing you into the permanent fabric of the universe. The most powerful human and all that he has done, is as meaningless as the most helpless and shortest lived; when the last historian dies even Caesar's name shall be dust. Your life effectively has no lasting consequences, so try and do what you actually wish.
I don't personally subscribe to such a worldview but lots of people will find freedom or comfort in that.
I'm in my twenties now, periodically overwhelmed by the current and potential future misery of the world. However, I have lately been able to cope with my misery by realizing that my misery is only subjective, which softens it. Perhaps that does not make my feelings misery at all.