Anyone who has trained for an event such as a marathon, or any other type of sport, knows that physical training is important. Without it, it is next to impossible to reach the goals you set. But, as important as physical training is, its value is limited to this life only. Spiritual training, or godliness, is of much greater value. It is profitable for all things, not just in this life, which is temporary, but in the life ahead of us, which is eternal. (1 Timothy 4:8)
As believers, we need spiritual training. We need to prepare ourselves for eternity. How do we do that? We need to spend time in the Word, reading it, studying it, and letting it abide in our hearts. We need to spend time with other believers, worshiping together, working together, and loving and caring for each other. Most importantly, we need to spend time with God. We need to seek His presence, not just on Sundays, but every day of the week. We need to spend time talking to God and listening to Him. And, we need to worship Him always, not just when we feel like it, but even when we don't.
Physical training is good for our bodies. It's important to keep our bodies physically fit. But, until the day that the Lord returns and we are given bodies that are imperishable, the bodies we now have will perish. On the other hand, our souls will live for eternity. How that eternity looks for us is dependent on our spiritual fitness. For that reason, although we should keep our bodies fit, it is far more important to keep our souls fit.