At the foot of the mountain, a large crowd was waiting for them. A man came and knelt before Jesus and said, 15 “Lord, have mercy on my son. He has seizures and suffers terribly. He often falls into the fire or into the water. 16 So I brought him to your disciples, but they couldn’t heal him.”
17 Jesus said,
19 Afterward the disciples asked Jesus privately, “Why couldn’t we cast out that demon?”20
In verse17 Jesus says "How long must I put up with you!" He'd been up the mountain having a great experience with God, and when he came down, he found that his disciples couldn't help someone in need. Yet Jesus didn't let his frustration come between him and the glory of God. He still met the needs of the father and the boy, driving out the demon. Then, once his work was done, he set his frustration aside and returned to his instruction of the disciples. His disciples had lost focus, and Jesus patiently showed them what they needed to do.
I have to admit, thinking about being the one to frustrate Jesus is a bit nerving. Perhaps there are times when we pay too much attention to the task and changes at hand. Instead, we should focus on The Lord, and he will prepare us properly for the task ahead. And by focusing on God and his timing, rather than our own, the people we are serving will be prepared for the changes ahead.