Seneca presents a powerful reframe of adversity - instead of seeing challenges as punishments or obstacles, we can view them as training for mental strength. Just as physical exercise builds muscle through resistance, mental challenges build character, resilience, and wisdom through difficulty. This doesn't mean seeking out unnecessary hardship, but it means approaching inevitable difficulties with the understanding that they're not just problems to endure but opportunities to develop capacities we'll need for future challenges. Each difficulty we navigate successfully increases our confidence and capability for the next one.