Indeed! We live by the power of the Holy Spirit, not by human strength. God's power doesn't fade as we get tired—provided we depend on him and not on our own strength.
If you listen to some songs (and not a little teaching as well), you will notice that they talk about "reaching the end of our own strength" and imply that is the point where God's help kicks in. That is garbage! That is self-help theology.
Without the sustaining power of the Holy Spirit, we don't have any strength to begin with!