A key to serving the Lord all the days of your life is spiritual fervor. The King James Bible refers to it as "fervent in spirit" and the Amplified Bible records it as "being aglow and burning with the Spirit". This flow of living by the Spirit of God is what will keep you seeking and serving Him continually.
We have the Holy Spirit as our guide in life and God has promised us that he will never leave us ( John 14:16-18 ). This is why he gave us the Holy Spirit as our counselor, to help us navigate this life by showing us all things, revealing the truth of God's word to us. As born again believers, we all have the Holy Spirit living inside, however we can choose the degree to which we flow in Him. Without a close fellowship with the Lord, being guided by His Spirit, it is easy to get distracted along the way and wrapped up in what the world has to offer. But if we live by the Spirit we will not have any desire to gratify the things of the flesh ( Romans 8:5 ).
This is key, because if we are to serve the Lord all the days of our lives being zealous for Him, then this can only be accomplished supernaturally. If we try to do this in the natural realm, in our own efforts, we have set ourselves up for failure. It takes the focus off God and places it on us and what we can do for him. Ours lives then become a yo-yo between trying to live for God and being persuaded by the world around us.
However, if we solely seek the Lord and keep ourselves stirred up by reading the word, praying in the Holy Spirit and listening and fellowshipping with God all the time, then our service and worship is a lifestyle not something we do to please God. We are simply living as an extension of Him. Directed and guided by His spirit in all things. Our spiritual fervor is a byproduct of knowing God and walking with him. Nothing is this world can shake it. No temptation of the flesh can distract us, because we are flowing in the Holy Spirit in tune to God.
Today, it is my prayer that you allow the Holy Spirit to flow through you guiding and directing your steps. Let Him encourage and build you up so that your zeal will always be for the Lord. May you serve Him out of love not obligation all the days of your life, amen.