A mantra is not a description of your current mood. Monks repeat theirs on the mornings they feel nothing whatsoever; the repetition is the entire technology.
Which takes some pressure off. You do not have to believe it at seven in the morning with a day ahead that looks exactly like yesterday. You only have to say it, the way you brush your teeth without holding an opinion about enamel, and let the saying accumulate somewhere below the level you can check.