If you ignore it, you may meet it three-fourths of the way down the runway, bringing the sinking feeling that you won't make it over the trees. It's no pun to say that it is not an uplifting experience. The wings, elevators, rudder and propeller are all airfoils responding to air flow. They lift, guide and power an aircraft. When the density altitude is high, the performance of airfoils is degraded, giving less lift and thrust.
Engine power is reduced due to less dense air.
Low air pressure in the cylinders requires less fuel to give the ideal mixture, but less fuel and air means less power. Maximum aircraft performance is at sea level on a standard day. Turbocharged engines provide sea level thrust to their critical altitude, but the airfoils on a turbocharged aircraft suffer from density altitude just like those on the normally aspirated aircraft. All the rest are higher density altitude days. High density altitude requires more runway for take off, landing and climbs.