Not that I have already attained, or am already perfected; but I press on, that I may lay hold of that for which Christ Jesus has also laid hold of me.
If anyone in the days of the early church had times they may have felt like quitting and giving up it would have been the apostle Paul, but he did not. Paul had the goal of fulfilling all that Christ had laid hold of for him as his focus. What often hinders us from pressing on is looking to or focusing on the past. In the very next verse Paul stated there was one thing he had learned, to forget what is behind and press toward the goal of what Christ has ahead. Far to often we tend to always look to our past instead of simply releasing it and letting it go.
If you are looking to your past you are not moving forward to the promise. Every promise we have been given through Christ Jesus for our life awaits us. We have to press on in faith to obtain those promises. The first generation of the children of Israel did not enter the promise land for they kept looking back to Egypt. God got them out of Egypt, but He could not get Egypt out of them. We have been delivered from Egypt and made new on the inside. Start looking to this new man you now are in Christ Jesus.
This is the problem with many believers today. They do not press into this new man they have now become. They continue to see themselves through the old fleshly nature instead of who God says they now are. You have to press forward by renewing your mind to this new you to become transformed on the outside. Stop looking at the old fleshly nature, he is dead and gone. Start pressing into the Truth of the new you, for you are a new creation in Christ Jesus.