C++ Probleme bei Implementierung von verketteter Liste

class MyList {

	public:
		bool isEmpty();
		void shift(wstring newElement);
		void printElements();

	private:
		wstring head = L"";
		MyList *tail = NULL;

};

/* check if the list is empty */
bool MyList::isEmpty() {
	return (this->head.empty());
}

/* add an element at the beginning of the list */
void MyList::shift(wstring newElement) {
	if (!isEmpty()) {
		// add the head to the existing tail
		if (this->tail != NULL) {
			(this->tail)->shift(this->head);
		} else { // create a new tail
			MyList newTail;
			newTail.shift(this->head);
			this->tail = &newTail;
		}
	}
	this->head = newElement;
}

/* print the elements of the list on the console */
void MyList::printElements() {
	if (isEmpty()) {
		wcout << L"|" << endl;
	} else {
		wcout << L"| " << this->head << L" ";
		if (this->tail != NULL) {
			 (this->tail)->printElements();
		} else {
			wcout << L"|" << endl;
		}
	}
}

MyList* newTail = new MyList();
newTail->shift(this->head);
this->tail = newTail;

bool isEmpty() const;
void printElements() const;

{
    MyList firstList;

    // Hier folgt Code, der firstList mit Inhalt befüllt ...
    // ...

    // Jetzt passiert etwas in diesem Falle fatales.
    MyList copyOfFirstList = firstList;

    // Und jetzt wird der Gültigkeitsbereich von firstList und copyOfFirstList  verlassen. Beide Listen werden zerstört.
    // ...
    // *RUMMS!!!* Verstehst du warum?
}