Reason for long stays at rest stops

I've had it a couple of times where I had two stops on the truck, and I get to one on Friday and it took them too long, so the second stop was closed til Monday, had to wait the weekend.
Also dropped whole cargo on Friday, and had to wait til Monday to pick up a load for the same reason. Often poor planning on dispatchers part, or poor time management on me to get the load there. Learning curve as it was. Only been out there 4 months but getting better each time.