Faith is not static. It can grow, and it can shrink. The good news is that growth is not mysterious — it happens through fairly ordinary means.
Four things that grow faith
Hearing. Faith comes by hearing God's word. Read it, and sit under teaching that takes it seriously.
Remembering. Write down what God does. Memory is short and discouragement is loud. A written record of answered prayer will steady you on a bad day more than almost anything else.
Stepping out. Faith grows by use, like a muscle. Do the small obedient thing you have been putting off. Give when it is inconvenient. Have the conversation you are afraid of.
Company. You will absorb the faith of the people you spend time with. Choose some of them on purpose.
What shrinks faith
Isolation. Comparison. Living on other people's spiritual experience instead of your own. And feeding constantly on things that leave you anxious and cynical.
You do not have to be dramatic about this. Just notice what leaves you trusting God more, and what leaves you trusting Him less, and adjust accordingly.
Be patient with yourself
Nobody grows in a straight line. There will be seasons that feel like standing still, and then you will look back after a year and realise how far you came.
Keep walking. That is the whole instruction.