About save the MPU6050 Data in SD card

As the topic, how can I save a huge and continuous data to the SD card (like MPU6050 accelerometer data.

The demo program teach me to save the print data once only.

#include <SD.h>

File myFile;

void setup() {
// Open serial communications and wait for port to open:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
}

Serial.print("Initializing SD card...");

if (!SD.begin(4)) {
Serial.println("initialization failed!");
return;
}
Serial.println("initialization done.");

// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.
myFile = SD.open("test.txt", FILE_WRITE);

// if the file opened okay, write to it:
if (myFile) {
Serial.print("Writing to test.txt...");
myFile.println("testing 1, 2, 3.");
// close the file:
myFile.close();
Serial.println("done.");
} else {
// if the file didn't open, print an error:
Serial.println("error opening test.txt");
}

// re-open the file for reading:
myFile = SD.open("test.txt");
if (myFile) {
Serial.println("test.txt:");

// read from the file until there's nothing else in it:
while (myFile.available()) {
Serial.write(myFile.read());
}
// close the file:
myFile.close();
} else {
// if the file didn't open, print an error:
Serial.println("error opening test.txt");
}
}

The demo program teach me to save the print data once only.

If you can do something that takes three steps (open the file, write the data, close the file), you should be able to apply that to something that takes more than three steps (open the file, while(!boredOutOfSkull) { readMPUData(); writeMPUData(); }, close the file).

Thank you so much, but I want to know what is the meaning of "!boredOutOfSkull"?