Time to get out for some longer rides and consider.
1 Is you bike, tyres and chain in good condition? Puncture repairs?
2 Will your kit be good on a rainy dark evening. Waterproof and warm?
3 Snacks, drinks. How will you keep hydrated and you energy levels up. It's best to snack rather than eat a big meal.
4 What is the range of your bike? Where will you fill up when check points are too far apart.
5 What is your target eta at each checkpoint. You'll them know if you are dropping behind schedule and consider your options.
The point of the ride is to complete it. Not to pop out for lunch.
Having said that there is no shame in admitting it is too much on the day and leaving it to try again another time.