Praxis Grammatica - Promises, Promises, in Latin

The 17th century Praxis Grammatica tells you who how "I" will behave in the future:

[ 28 ] Ero posthac diligentior. [English Translation]

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Praxis Grammatica gives great examples of Latin sentences in the guise of wondrously useful advice. Please feel free to post your interpretation of this bit of Latin and when it would be used.