Paying attention - acting or reacting?

So, the other day, on the way home from work, I had this experience where I correctly evaluated a situation but chose not to take evasive action. Turned out fine, no problem at all but it was a situation that given again, I would have done differently. Here is a crudely drawn map showing the situation.

I am the yellow motorcycle following a safe distance behind the red car. Following a safe distance behind me is the purple car. There is no other traffic behind it. The red car signaled its intention to turn right. I travel this route every day and am usually in this lane and am anticipating cars making this turn, either onto the street or into the parking lot of the vet on the corner. As I scanned in anticipation, I noticed the blue car wishing to leave the parking lot and make the right turn onto Broadway. What I've determined is that the red car will probably also see the blue one and might make the turn more slowly into the parking lot and that I would have enough time to slow down. I've also determined that there is no traffic in the lane to my left and that it would be safe to change lanes should the red car decide to stop. I've also determined that the purple car is also slowing and is also far enough behind me to not pose a problem should I change lanes.

All of those deductions were accurate and indeed the red car did slow a lot and nearly came to a stop wishing to allow the blue car to leave the parking lot before it entered.

However, despite the fact that I made the proper evaluation, I maintained my position and did not slow nearly enough in time for all of it to play out. I didn't have to slam on the brakes and didn't even almost rear end the red car, but I put myself in a position that I should not have been in. I didn't react to my own correct interpretation of the situation.

Was I distracted? Not really listening to myself? Was I simply not really paying attention? Thinking about it shortly after the event played out, and it was hardly an event, I think I was just thinking of too many other things. I was not yet out of town but was still processing my day while on the bike. What I should have been doing was processing my ride as it was happening.

And it wasn't a close call by any stretch but just something that made me realize that I wasn't listening or paying attention. I was too comfortable in the predictability of the route perhaps. I need to not just pay attention but be fully engaged and ready to act and not just react.

A good lesson and not a painful one.