What keeps us from Decisions - for example, "Should I commit to long-term mission" - isn't a lack of ability to make a decision. It's the decisions we have made (past Decisions) or the Decisions we might make or want to make.
Many (most?) of these decisions come out of Defaults or Desires.
We can decry the Defaults and Desires that lead to choices that deny the Decision we'd like to see people make. But that won't get them to change their Decisions.
Instead, I suggest we need to help people engage with past decisions and their existing desires, and see how these might still "work" in the context of mission.
If people don't want to commit to 20 years, then let's frame a mission career as a succession of 2-year "terms," for example.
If people are afraid of not finding a spouse, let's talk about point to successful courtships and marriages.
If people are afraid for their children, let's talk about the good and bad of children growing up on the field.
Don't give into the temptation to denigrate someone's desires or decisions.