Psalms 102:3

For my days are consumed like smoke, and my bones are burned as an hearth.

Human days vanish like smoke, for life passes quickly and is brief and frail, fading and vanishing away. Bones are like a burning hearth, burned and dried up and consumed, expressing distress and bodily weakness. In this picture David feels his own life fading quickly and his body consumed by distress, in loneliness and suffering.

The psalm is expressly for the afflicted, belonging with psalms of the sorrows and afflictions of the Hebrew captives. Those psalms also give encouragement and assurance of divine help, with hope of final deliverance from persecutors. The prayer sets brief and frail human life before God's unending years.

That prayer asks God for strength and guidance, recognizing that people need help to follow the promptings of His Spirit. Even in such loneliness and suffering the sufferer is not forgotten, for God tenderly cares for him. The verse belongs to a plea for mercy that every true believer may make his own, since earthly life vanishing like smoke leaves people to face death.