And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it.
We are not called to build the church, Jesus is going to build His church, and it will be all that He desires for it to be. We can partake of that only to the degree that we abide in Him.
We will only be frustrated with the people if our hope has been wrongly placed in them, when our hope is rightly placed on the Lord, we will not be overly discouraged when men fail us, or overly encouraged when they do well.
The finished work of God has already been accomplished, which is Jesus Christ Himself and all that we have been called to do is abide in Him, and point others to Him.
This is the true call of every believer, to become like Him for the Lord works in us both to do and to will of his good pleasure.