Tamasic happiness deludes the self both at the beginning and at the end. There is no redemptive arc here — no bitter start leading to sweetness, and no sweet start at all. It is born from excessive sleep, laziness, and carelessness, and it keeps the person trapped in dullness throughout.
Spending the entire day in bed, avoiding responsibilities, drifting through life without direction — there is a kind of 'comfort' in this. But it is not happiness; it is numbness. The person mistakes the absence of effort for the presence of peace.
Among the three types of happiness, tamasic is the most harmful. At least rajasic happiness offers a moment of genuine pleasure at the start. Tamasic happiness offers only the illusion of comfort — a fog that never lifts.