Jesus had entered a village after a period of traveling and teaching. Martha opened her home for him to stay in. It was customary in these times to open your home for traveling teachers and provide hospitality to them. While Martha worked around her house, preparing things for Jesus' stay, her sister, Mary, did not help Martha prepare but sat at Jesus' feet as he taught her.
This, of course, brought on a complaint from Martha that Mary was not helping. In replying to her, Jesus stated clearly that Mary had chosen the "one thing" that was "necessary" (10:42). The implication is that Martha's busywork was unnecessary, while learning from and sitting with Jesus was the "good portion." In fact, Martha's busy-ness is twice called out in this passage, once by Luke ("Martha was distracted with much serving"; 10:40) and once by Jesus, who said to Martha, "you are anxious and troubled about many things" (10:41).
Think about this: Martha was preparing things for Jesus. She was working on good things. She was involved in ministry. But Jesus did not advocate more work, but rest. The one thing that was necessary was to rest and listen to him.
Martha represents a follower of Jesus. She represents us. How often are we distracted from listening to Jesus by being (over-)involved in good things? How many of us are anxious over what is or is not happening in the church or in our spheres of ministry? When this happens, we tend to work more, to try to control more or get more done, which leads to more distraction and more anxiety.
Instead, Jesus says, practice the necessary thing and rest in him. Sit as his feet. Pray. Read the Bible. Take a walk. Take a break.
The antidote to anxiety is not action but awareness. Balance work with rest. Take time for yourself to simply be with Jesus. Learn his rhythm of balancing being with God and serving others.