I knew of a case of someone who had believed and there had been changes in their life, but they lacked assurance. Then someone they were close to went through an illness, and the grace of God was so clearly displayed in this sickness that this Christian lady received deeper assurance through this.
We must look to the Lord for a positive outcome of all events so that we become optimists. We are optimists if we belong to Christ from an eternal perspective, whatever the natural pessimism we are naturally endowed with.