When do we need endurance?
We need it when things are going absolutely perfectly, and we need it when things are going absolutely horribly, because there is a different threat to faith in both cases.
When I say "endurance" I mean the endurance of faith, and when I say "faith" I mean a profound deep satisfaction in all that God is for us in Jesus. And two things threaten such faith: pleasure and pain.
When pleasure comes fast and furious, months and years without end, the danger is that we begin to trust in, rely upon, and be satisfied by all the good things. And when pleasures go and pain comes, the danger is that we throw our confidence in God away. We get mad at God and say, "Where are you!" Instead of making him the treasure in our pain, we say, "You were supposed to give me something better than pain, and since you didn't I'm out of here." And that's the threat to faith.
So we need endurance all the time. Persevering in faith has to happen every day.
I suppose over the years of my ministry, one of my most common prayers has been, "Lord keep me faithful. Please. Today, tomorrow, over the years: keep me faithful. Don't let me begin to coast, become lazy, or become cavalier about the ministry. Don't let me become bored with the ministry or take it so for granted that I begin to have other hobbies that consume more of my emotional energy."
It's really sad when you find pastors especially, and Christians in general, for whom the ministry becomes what they do when they're on autopilot. But what they do when they're really engaged is play. And they're just looking for their day off, their weekend, their hobby, boat, toys, cabin, getaways, computers, and new gadgets. That's tragic.
Jesus Christ and his purposes for us and his ministry should be the thing that gets all of our energy. So endurance is the battle that keeps us going at that.