Faith is one of those words that has been stretched so far it has almost stopped meaning anything. People use it for optimism, for positive thinking, for a personality type. So it is worth going back to the definition Scripture actually gives.
Faith is not a feeling you generate. It is confidence in what God has said, solid enough to act on before you can see it.
Hebrews 11:1 says faith is the substance of things hoped for, the evidence of things not seen.
Two words carry the weight there. Substance and evidence. Both are concrete words. Neither one describes a feeling.
Faith, biblically, is not working yourself into certainty. It is treating what God has said as solid enough to act on, before you can see it. Which means faith always has an object. It is not belief in belief. It is confidence in a specific person who has made specific commitments.
That distinction matters enormously in practice.
If faith is a feeling you generate, then a bad week is a spiritual failure and you are responsible for manufacturing more. That is exhausting, and it is not what the chapter describes. Hebrews 11 goes on to list people who obeyed while confused, who waited decades, who died without receiving what was promised, and it calls all of that faith.
If faith is confidence in God's character and word, then the question in a hard season is not do I feel strong. It is what has he actually said, and am I going to live like it is true.
That is a question you can answer on a bad day.
Faith is not the absence of doubt. It is the decision about who gets the final word when doubt shows up.