Be Seen In Traffic
Now that winter is definitely probably almost nearly here (currently sunny & just below 20 °C here is Croatia), the chances are that you’re going to end up riding at night. Unless you are actually a Bike Ninja, and on some sort of assassination mission, it’s a good idea to make yourself as visible as possible - even if you ride along routes that are free of motorised traffic. Having another bike ride into you, or a pedestrian step right into your path can ruin a good ride home!
The obvious thing to do is make sure you have good, bright lights on your bike (it’s also a legal requirement in the UK after dark if you’re on the road), and to make sure that your reflectors are clear of grime. Reflective clothing can help too - and it needn’t be bright yellow either - you can get subtle clothing with Scotchlight tape built in, which’ll light up nice & bright in headlamps. Of course, for day-time riding, you might want to go for brighter colours. I don’t particularly recommend a mid-grey outfit on a foggy day, no matter how much Scothlight is has in the piping!
Be seen, and you’ve one less chance ending up laying on the road, and hearing the words, "Sorry Mate, I Didn’t See You".
To avoid being a SMIDSY statistic, some cyclists go to extreme lengths though . . .