Occasionally Pattern, or any app for that matter, may crash. Do not panic. While repeated crashes are an issue, a crash once in a while is normal.
Simply power off your smartphone by holding down the power button of your device. Once your phone has turned off, wait 5 seconds. Then, click the power button again in order to turn the device on.
The example shown below is for the iPhone, but keep in mind your phone may look different when you are powering it down.
If you are on a device running the latest version of Android, you should see an Android logo as your phone powers on. Once your phone is totally powered on, you can begin to access Pattern app normally.
If you are on an iPhone, you should see an Apple logo as your phone powers on. Once the phone is totally powered on, make sure you open Pattern app immediately. If your Pattern app has not been opened at least once, you will not receive notifications or reminders about your daily plan.