If we constantly identify with the aches, pains, and fatigue of our body, we will give in and not do the full work of Christ. We offered our body as a living sacrifice because it wasn't willing to do righteousness and stop doing misdeeds of the flesh (sin). Taking up our cross and following Jesus is dealing with the body's frailty rather than its sinning characteristics. Jesus already died for our sins on His cross. Our cross isn't going to do anything for that. This same Scripture goes on to say: "For whoever wants to save his life will lose it, but whoever loses his life for Me will find it." This is talking about giving our life of Time, Intellect, Money, and Effort over to God. Reserving our life here on earth for our own interests, cheats us out of being mightily used for God. We must die out to self and give our life completely over to God. Even if we're only spending time on things that aren't sin, it still doesn't make us live a life of Christ's ministry. There are a lot of things in this world that are neutral as it relates to sin. When we give up everything that doesn't fall into God's will and way, is when we have moved into Ministerial Spiritual Warfare. That is when we experience Christ's ministry flowing through us. But, as Christ's ministry starts flowing through us, we experience persecution. That doesn't sound like fun, but it can be.