If I am honest doing good can be tiring. I look back on my last position as Pastor and I wonder how I did all the things I did!
The truth is though we are called by God and empowered by the Holy Spirit when we do a role like Pastor of a church. And often the gaps we have in our skills or energy are filled in by God.
One key I found to not grow weary in doing good is to start the day with God. It is so easy to do all the things on your to do list, without checking in with God first. It is just so vital to be with God first, before starting His work.
As I type I think of the example of Jesus. A number of times we read in Scripture that Jesus went off to a solitary place to be with His Father. He checked in and only did what He saw the Father doing.
Today I would encourage you to check in with God before you start your work. Spend some time in prayer and in the Word, before you go to work or church.
For me, checking in with God first brings the heavenly energy and heavenly insight I need to do His work. We need this to reap the promised harvest.