As many commentators have said regarding this passage, Peter’s faith is much like ours, small and incomplete, a mixture of trust and doubt. Nevertheless, God does not wait for us to have perfect faith before He saves us. The mere presence of authentic trust is required, and periods of doubt say nothing about the legitimacy of our faith. No matter the fervor of your trust this day, know that Jesus is a Savior who rescues those who struggle with doubt.
For further study:
The Bible in a year: