2 Corinthians 6:5 In stripes, in imprisonments, in tumults, in labours, in watchings, in fastings;

Whether it was the abstinence of food to focus upon prayer or the Word or the case of the lack of the means for subsistence, the Apostle Paul shared the rigours of engagement in the gospel work.

Acts 14:21-23 And when they had preached the gospel to that city, and had taught many, they returned again to Lystra, and to Iconium, and Antioch, Confirming the souls of the disciples, and exhorting them to continue in the faith, and that we must through much tribulation enter into the kingdom of God. And when they had ordained them elders in every church, and had prayed with fasting, they commended them to the Lord, on whom they believed.