Tobit was "very much mistaken" (see Mk 12:27). He believed he should die because he would never be cured of his blindness or have happiness again in his marriage (Tb 3:6).
Sarah was "very much mistaken." She thought of committing suicide (Tb 3:10) because she didn't believe she would ever be delivered from the demon, Asmodeus, who killed her seven husbands on their wedding nights (Tb 3:8).
The Sadducees were "very much mistaken." They did not believe that we will rise from the dead (Mk 12:18). Therefore, they had no hope for the future and little joy in the present.
All these people were "badly misled" because they failed to understand the power of God (Mk 12:24). If we don't believe in God's power to heal the sick, restore marriages, drive out demons, and raise the dead, we will repeatedly come to the wrong conclusions. Ignorant of God's power, we will give up when we should go on, and settle for a culture of death rather than create a new civilization of love and life.
Daily ask for the gift of faith. Daily read about God's power in the Scriptures. The Lord will grace you with faith through hearing His word (Rm 10:17). Know and believe in God's power. In the light of His power, you will know the truth and never be "very much mistaken."