It's better to derive or calculate state, rather than unnecessarily mirror it.
For example, given a form that accepts a firstName and lastName, don't additionally store this data in a third state value of fullName. Instead, calculate fullName as needed by concatenating other state variables during rendering.
This makes your code faster (you avoid the extra “cascading” updates), simpler (you remove some code, [[20200307105301-dry]]), and less error-prone (you avoid bugs caused by different state variables getting out of sync with each other).