Here is his thoughts on missionary preparedness:
Mental, emotional, and physical preparedness is one thing. Spiritual preparedness is another.. As far as the first three go... almost impossible. The mission is nothing like you expect. You get thrown into it. Follow the guidance in the paperwork all missionaries are given. Fear/anxiousness is normal. Don't worry. But none of that unpreparedness will be a problem. The Lord will take care of it. His arm is always extended.
Spiritually prepared: my recipe, Scripture and PMG study along with much prayer and fasting and weekly trips to the temple. There's a talk given by Elder Holland about worthiness. They actually made a youth video about it. I think it's called,"stay within the lines" or something like that.
"...Well, the Lord has drawn lines of worthiness for those called to labor with Him in this work. No missionary can be unrepentant of sexual transgression or profane language or pornographic indulgence and then expect to challenge others to repent of those very things! You can’t do that. The Spirit will not be with you, and the words will choke in your throat as you speak them. You cannot travel down what Lehi called “forbidden paths”5 and expect to guide others to the “strait and narrow”6 one—it can’t be done.