One of his points reiterated some teaching I'd also digested from "My Utmost For His Highest" by Oswald Chambers. Keller asserted that while God plans out our life, many of the decisions are up to us. Whether we decide one way or another, God will plan our lives accordingly, but we are responsible for what we decide. Chambers likewise asserted that God doesn't call some people to missions and not others, but that he calls all and the decision is up to us.
In Isaiah 6, the prophet over hears God asking the question "Whom shall I send? And who will go for us?" Isaiah responds with "Here am I. Send me!" God didn't single out the prophet, but the prophet saw the need and responded with a willing spirit. With Penn State, I saw the need for additional staff on campus. After seeking to minister to college students for several years, and aiming to be campus ministry staff full time, the choice was clear. My only alternative consisted of remaining on the sidelines of full time ministry, and continuing to live a life that would have been more self serving and less dependent on God through faith.
Likewise with Joanna. During college I came to see that the soul mate idea was complete fiction. There is no one perfect person out there for everybody. Paul himself asserted that for some people, it is better to remain unmarried in order to focus solely on God's kingdom without the commitments a family makes. He also asserts that for some people, it is better to marry if they can impact God's kingdom in a more holy way together than separate. Every relationship requires work, trust, and commitment to meet the needs of your spouse exclusively while also having many of your needs exclusively met in return. Spouses can't meet every need, and indeed God must be the well you draw from first. You also need to keep your base of friends and family. But meeting needs requires work.
With Joanna, I saw early on her heart to worship God. I saw a heart that was close to Him, and drew close on a consistent basis through prayer, scripture, teaching, and being involved in missions. I saw in her a spirit I could truly trust, and someone who would equally desire to minister to others in her own way (currently through nursing). Our purpose drew from Ephesians 5, my aim being to ultimately help her to bring more glory to God.
After several months of intentional courting, I came to a point of believing I could better serve Joanna as a husband, and if she was willing, she as my wife. Thus I chose to propose. Marriage is no light decision to be made, nor did I decide lightly. But I decided with a Godly purpose. When you make decisions based on scripture, out of consideration for others, and what will be best for yourself, there's often no wrong choice to be made.