Your activity goal to show your weekly progress. A new week begins every Sunday morning. If you have 4 out of 5 activities done for the week on Saturday night, you'll see 0 out of 5 completed for the following week on Sunday morning. You can monitor each week's progress in the Number of Activities indicator highlighted below.
If you find you're unable to achieve your goal for a few weeks in a row, you may feel better adjusting your goal. Just tap on the same box to see the screen below to easily adjust your goals.