"Therefore they did forsake all their sins, and their abominations, and their whoredoms, and did serve God with all diligence day and night."
3 Nephi 5:3
Most of what we have to sacrifice for God is of this sort. We have to give up our sins to know God. And, you know... it isn't a punishment sort of a thing. It is just like you have to wash all the moldy leftovers out of the frying pan before you cook some nice french toast for breakfast. It is a clear some space for goodness sort of thing. If our minds and our hearts are filled with the past, with all of the bad things we've seen and read and done... how are we going to think about God, and eternity... and all the interesting aspects of switching over from the "time zone" to eternity? :) These people in 3rd Nephi had to do their forsaking before they could do their serving. It is a prerequisite. We can't sin and serve at the same time. So often we want the blessings of service before we let go of sin... we want God to prove to us how good it is before we taste it. But, we can't avoid the work... we have to clean up our lives before we can invite God over. We have to commit, and dedicate ourselves to the relationship before we get any of the benefits. We can't just go to God halfway.