It's quite a good risk.
I fly a certificated, well maintained aircraft powered by an single agricultural Lycoming. I've had it for over 30 years and some thousands of hours. I've flown it to several continents, and across various oceans.
I can't say it's never given trouble in flight but it's never failed to get me to an airfield.
The fraction of time I fly it at night or in hard IFR is quite small. I don't seek out these conditions but if they turn up I just go.
The aircraft doesn't know it shouldn't fail today more than any other. It's unlikely it will fail on any day, it's VERY unlikely to choose a bad day since there are not that many really bad days.
Bill