Jesus contrasted two roads: the wide gate and broad way that lead to destruction, and the strait gate and narrow way that lead to life, which few find. The narrow gate is the way of following him.
The image is not meant to discourage but to call for decision. The narrow way is demanding but leads to life; Jesus himself is the door through which we enter it.
The Narrow Gate in Scripture
Because strait is the gate, and narrow is the way, which leadeth unto life, and few there be that find it.