Jesus says the way that leads to life is hard. The word he uses belongs to a family of words about pressure, suffering, and persecution. It is not merely that the Christian life takes discipline, though it does. It is that the road to life can lead you straight into opposition, and often will.
Some of us were sold the opposite. We were told that if we came to Jesus our problems would shrink and our path would smooth out. Then the road turned uphill and we assumed we had taken a wrong turn. But look back two chapters in this same sermon. Blessed are those who are persecuted for righteousness’ sake, for theirs is the kingdom of heaven. That is not a footnote. That is Jesus telling us up front what this will cost.
Now look at what Luke calls strengthening. Paul had just been stoned and dragged out of Lystra and left for dead. He got up, went back into the city, and circled around to the young churches to strengthen them. And the strengthening word he brought was this: through many tribulations we must enter the kingdom of God. Not around them. Through them. Ben Witherington and others note the deliberate preposition. God is not primarily in the business of arranging escapes. He is in the business of walking his people through.
So one of the ways you know you are on the right road is that it is hard. Sin feels like coasting downhill; repentance feels like riding uphill. Your own fallen heart pulls against you, and sometimes the whole current of the world pulls with it. That resistance is not evidence of failure. It is the friction of walking against the grain toward life.