Some agility work to go along with the sprint intervals. Keep moving during the rest. If you can keep a slow jog or airborne shuffle up during the 300’s then do so. You should be hitting the 400’s hard. Attempt to control your breathing and return to nasal breathing during the recovery movement, if possible. You can do it, focus.
American Made Mentality Training quote from the book “Mind Gym.” I highly recommend it if you’re looking for a quick read with a ton of great knowledge bombs.