Dallin H. Oaks, “Timing,” Ensign, Oct 2003, 10–17
I reminded the missionaries that some of our most important plans cannot be brought to pass without the agency and actions of others. A missionary cannot baptize five persons this month without the agency and action of five other persons. A missionary can plan and work and do all within his or her power, but the desired result will depend upon the additional agency and action of others.
Consequently, a missionary’s goals ought to be based upon the missionary’s personal agency and action, not upon the agency or action of others.
I don't remember how I heard it originally, but I remember thinking AMAZING! when I heard it. This quote has popped into my head various times throughout the past 5-6 years and I finally remembered to look it up at a time when I was at a computer and had the time to search for it.
I remember as a missionary being told to make a goal for how many people we were to baptize the coming month. We were to pray about it and come to a mutual decision w/ our companion. I never felt good about it, not bad per say, but never like, "Yes, it will be 5 this month if we do our part." Then, during the times when we got less than our goal we would beat ourselves up for not doing our part. Why else would we have not achieved our part of the "covenant?" The Lord doesn't falter on his side.
My brother-in-law is on a mission and I have heard him say a similar thing once about his setting goals for how many people will get baptized. I'm surprised this talk hasn't been photocopied and passed around in mass amongst the missionaries like other things.
Late addition:
I am similarly surprised to hear the brethren say repeatedly that we need to simplify by having less meetings and allowing people to be with their families more. Despite the repetition over the pulpit, this hasn't seemed to sink in enough. I know that people do both of these errors with good intentions and sometimes it can be hard to change the boat when it has so much inertia.
Another problem that I have seen in my life similar to setting goals based on other people's agency is when I place my expectations on other people's agency. A famous LDS psychologist and author, Bro. Lund recently mentioned in an adult meeting in our stake that all frustration comes from unmet expectations. I don't know that we can necessarily avoid having our expectations sometimes based in other people's agency, but as GI Joe said, "Knowing is half the battle!" Recognizing this may help us to own our expectations and therefore reduce the amount of things causing frustrations in our life.