Listen to your body. TRY, but if you're getting crushed, throw it into zone 2, ride some endurance, and finish out the block.
Some caveats: are you in race season? That changes some things. And if you're EXHAUSTED, shift into a rest week and figure out why. But in general, many times you can sub out those two interval sessions with endurance riding, cap off with some nice weekend rides, and then soak up all that training during the rest week!
