Life isn't suffering, life is... I dunno. But desire causes suffering. Desire is the birth of samsara or suffering through infinite potential desiring manifestation. Form is born of desire for form. Suffering is born from impermanence. All structures are finite and eventually cause suffering. If you don't get what you want, you suffer. If you get what you don't want, you suffer. If you get what you want, you suffer when it's gone.