As with most asana, it takes time to build endurance. Keep your elbows close together, otherwise your torso will slide onto the floor between your forearms. Don’t hurry! It is fine to remain anywhere in the various stages of entry and try again another day. Your breath is the greatest indicator that you are safe in an asana. If you’re restricting, holding, or forcing your breath, it’s time to exit the pose and try again later.