A common thing I hear from cyclists is "Oh, I've never done 100km, so I don't know if I can" or "150km! That's too far for me."
On my first sportive, years ago, I was really focussed on the distance - would I be able to get around? And what would happen if I couldn't?
And probably, at that time, my longest bike ride was 50km - so 150 was certainly unknown territory.
Distance myth: The truth is - it doesn't matter!
You can do way more than you've ever done in training. You just keep going and so long as there's food and water on hand (and daylight) you can go much, much further than you have ever experienced.
Go for it!
Italian events and European climbs