I have a good ENTJ friend and I noticed something yesterday. He and I were asked to help someone move some large household items. He had a "meeting" planned at a certain time and so he couldn't stay and help as long as I could. Well, as time drew closer to his meeting, he became consumed by his pre-planned schedule. He was looking at his watch every 30 seconds. He literally could not get it off of his mind. It was to the point to where I wanted to just say, "Just leave. You're basically being ineffective NOW because you're thinking so much about 1 hour from now. You're really just getting in the way." I found it rather childish to be honest.
People bemoan the P function, saying that it's lazy and can't keep a schedule and it's flaky, etc, etc. I don't disagree that we can sometimes (if left unchecked) fall into these habits. But, one of the strengths of P, is that it is flexible. It goes with the flow. When life throws a curveball of sorts or when events/schedules change (which they do every single day), we don't panic or freak out. We just calmly go with the flow and play with the hand that is being dealt.
So, this isn't a rant on why P's are better than J's. I have a couple ENTJ friends who I think are great. I'm just wondering from the ENTJ perspective if this type of thing is something that you struggle with or get easily frustrated with. I've also had an ISTP tell me about a different ENTJ that, "he has everything planned out perfectly, and if things don't go according to his plan, then he freaks out and doesn't know what to do." That doesn't mean it's true, but it does mean that this is the way the ISTP is perceiving his reactions.