How can one be saved from the whispers of Satan that make life miserable and incite extremism or abandonment of prayer?

You must frequently seek refuge with Allah from the accursed Shaitan, acquire knowledge of Islamic law to distinguish sins, and consult scholars about what is unclear to you. As for what you are certain is a whisper from Shaitan, ignore it and pay no attention to it. Beware of responding to Shaitan by abandoning prayer or committing other sins; rather, persist in obeying Allah.