A too-soft mattress may leave you feeling like you’re sinking in quicksand, and make it difficult to turn and roll over. Because a soft mattress touches your entire front, back or side, some people complain that they’re too hot, especially in the summer months. When testing out a mattress, lay flat on your back. If you can slip your hand under your lower back, the mattress is too firm. If you feel your lower back curving downward and sinking into the mattress, then the mattress is too soft.