I've been driving for 30+ years, so I can't help you with the experience of learning at 40. But I can tell you what my dad told me when I started driving and what I will tell my children when they learn:
1. 90% of driving is predicting what the other drivers will do. Luckily most of them will follow the rules of the road, so you don't have to worry about those. You need to worry about the outliers. The driving part will become pretty automatic, it's the situational awareness that is most important.
2. There is only ever at most one person in front, one person in the back, and one person to each side. Those are the ones you need to worry about most. But you also need to know who will become those people soon, so make sure you look ahead and not at the road in front of you. And make sure you check your mirrors once in a while. When I was learning to drive, my dad would randomly quiz me, "is there a car to your left right now?" And I had to know without looking. Because in an emergency you need to already know which ways are clear.
But if you master these two things, you will be a better driver than most.
Good luck! And don't assume your age will make it hard -- the mechanics of driving are pretty straightforward with just a little bit of experience.