Consistency. I'm not talking about the how creamy the gravy is, I'm talking about doing things over and over and over again. I think it is one of the most fundamental principles of life. You must eat consistently. You can't over eat one day and not have to eat the rest of the week, it just doesn't work that way. You can't sleep for 24 hours then stay awake for the next three days with the same energy as sleeping 8 hours per night.
It's the secret that makes simple things illusive. People who want to lose weight have heard that you will lose weight if you exercise. That's only partially true. You will lose weight only if you exercise consistently. People who want to get out of debt know that they must make sacrifices of their wants and save to pay off debt. True, but it only works if you do that consistently. It's easy to try something one time. But it won't do anything for you until you've done it over and over during a period of time. Which is tricky, because that requires faith.
It takes faith to motivate yourself to do something difficult consistently when you're not seeing results. Humans like fairness when it's in our favor. It seems fair that if I do something one time, I should see a result one time. Not if I do something 100 times, I see a result. It's not always easy to eat healthy. But imagine that you had no evidence that eating healthy actually made you healthy... wouldn't it be harder? That's how it is for people (aka, all of us in some regard) who are inconsistent. We try something and we don't see it working. So we think it doesn't work and we give up.
It takes consistency to change. Effort exerted over a long period of time. We don't see the results for a while. But the cool thing is that with true change, the results keep coming and coming, consistently. :) If you start to try to be kinder to people, you may not notice any change immediately. It may be hard for you if you're used to being mean and sarcastic. Only over time will people begin to trust you more and open up to you. The fruits of your consistent kindness come later down the road in the form of strengthened friendships. One-time effort is not enough for a reward. True change is what gets results, and that is only accomplished through consistent effort. You won't have any huge change. Because change isn't huge. It's very small. It can only happen at the rate at which you grow. Living life and especially, having experiences determines that rate.
It takes consistency to see an increase in spirituality. You may feel the spirit if you're reading the scriptures one time. But only when you study consistently will you be more and more likely every day to have just the right scripture pop into your head when you need it. If you pray once, that is great, a bigger act of faith than not praying at all. But when you pray consistently, only then will you really see progress in your prayers. I think part of the reason for the delayed results for changing in life is for us to prove our intent. You wouldn't trust your usually selfish acquaintance if they were suddenly nice to you, because you'd suspect they have an ulterior motive, i.e., want the one-for-one ratio of blessing to effort. It takes maturity to be consistent, or rather I should say it builds maturity.
Our Heavenly Father also wants us to prove our intent. If we pray only once a month when we need a blessing, it's better than not praying at all (just like being nice once a month is better than not at all); but if we really want to have true results, we need to do it consistently. Because when something is hard, requiring us to sacrifice, it really brings out true intent. There are classes intended to "weed out" people in certain areas of study. Professors purposely make things difficult, requiring students to sacrifice. Only those with very strong and true intent will be sustained through all those consistent sacrifices and efforts. These are the students who deserve to get the ultimate reward of the career of their choice. Professors want all their students to succeed. But by pressuring them and requiring them to sacrifice the professors and students learn a lot about the students' true intent.
It's the same with our Heavenly Father. He purposely made this life difficult. He knows it requires work and discipline and sacrifice to serve, donate, pray, study and learn. But He wants to give us a chance to show our true intent through consistently doing those things anyway. All it requires is faith to actually do those things.