Grip strength is trainable. So is the ability to hang on when life gets slippery.

Endurance is an ability rather than a temperament, and abilities answer to practice. Holding on through something difficult gets built the way physical strength does: repeated exposure at a manageable load, with recovery in between. People who look naturally durable usually have a history you never saw. Nothing about your current capacity is fixed.

Choose one small uncomfortable thing and do it consistently for a month, not because discomfort is noble but because the habit generalizes. Keep the load sensible rather than heroic. Capacity built slowly is the kind that holds when something slips.