The Raspberry Pi has holes for mounting a reset header (marked RUN on the Raspberry Pi 3/2 and P6 on the Raspberry Pi 1 Model A and Model B Rev 2). The reset pin allows the device to be reset using a button rather than removing the micro USB connector each time to cycle the power:

To make use of it, you will need to solder a wire or pin header to the Raspberry Pi and connect a button to it (or briefly touch a wire between the two holes each time). Alternatively, we can extend our previous circuit, as shown in the following diagram:

We can add this extra button to our circuit, which can be connected to the reset header (this is the hole nearest the middle on the Raspberry Pi 3 or closest to the edge on other models). This pin, when temporarily pulled low by connecting to ground (such as the hole next to it or by another ground point, such as pin 6 of the GPIO header), will reset the Raspberry Pi and allow it to boot up again following a shutdown.