How could the martyrs during the reformation stand in peace, while dying at the stake, how could they endure the flames while singing hymns?

They had to know that God was with them, tell me how could they know for sure?   What are we actually saying here?...that we go by feeling and not by faith?  Certainly not!  But, we must be very careful not to just rely on an intellectual kind of faith either!

Acts 2  (v. 1) Now when the Day of Pentecost had fully come, they were all with one accord in one place. (v. 2) And suddenly there came a sound from heaven, as of a rushing mighty wind, and it filled the whole house where they were sitting. (v. 3) Then there appeared to them divided tongues, as of fire, and one sat upon each of them. (v. 4) And they were all filled with the Holy Spirit and began to speak with other tongues, as the Spirit gave them utterance.

The outpouring of the Holy Spirit on the Day of Pentecost was the former rain [and was wonderful], but the latter rain will be even more abundant.[1] 

Hos 6  (v. 3) .…Let us pursue the knowledge of the Lord.  His going forth is established as the morning; He will come to us like the rain, like the latter and former rain to the earth.  

How can you know when you are blessed with this peace?  Just believe when you are feeling anxious and somehow it just goes away?

John 14  (v. 16) ....I will pray the Father, and He shall give you another Comforter, that He may abide with you forever; [ KJV ]

Why comfort us, if we are not supposed to sense it anyways?...remember we go by faith and not by feeling right, or are we missing something?

(verse 17) even the Spirit of truth,...but ye know Him; for He dwelleth with you, and shall be in you. (v. 18) I will not leave you comfortless: I will come to you.  [ KJV ]

How can the Comforter, dwell with you and be in you, and you never sense it?  So, you just know Him by faith, is that right??

 Only the sense of God's presence can banish the fear that, for the timid child, would   make life a burden.  Let him fix in his memory the promise, "The angel of the Lord   encampeth round about them that fear him, and delivereth them" (Ps. 34:7).[2]  

Phil 4  (v. 7) and the peace of God, which surpasses all understanding, will guard your hearts and minds through Christ Jesus.

Does the "peace of God" guard your heart & mind by faith, or do you actually sense the peace?

 ....a great change had taken place in my mind.  It seemed to me that I could hardly be the same person that left my   father's house the previous evening....My heart was full of happiness....Faith now took possession of my heart. I felt an inexpressible love for God,...[3]

 I felt the assurance of an indwelling Saviour,...My peace and happiness was in such marked contrast with my former   gloom and anguish that it seemed to me as if my soul had been rescued from hell and transported to heaven.[3]