How the hardships are a part of our life?

Allah says in verse 36 of Al baqarah that we step down the Adam with Hawa for rest. If this universe is for rest then from where the hardships come in our life. How these 2 scenarios are variant from each other? Allah also says in verse 94:5 For Indeed with hardship will be ease. I want the science behind these verses how hardship and rest linked our brain?