There is a great deal of uncertainty when it comes to knowledge. The problem with the 'learning hysteria' arises essentially from a common misunderstanding about how cognition and the brain operates..
The truth is graduates are not really masters of the information they have assimilated, or at least this is not expected of them. One should first learn to remain humble. It does not matter how much you have retained. Instead it is your ability to seek-out, relate and interpret information that is of value.
When one learns for instance a new language, you do not go about trying to memorize every word in the vocabulary, nor does one attempt to facilitate a conversation by remembering every sentence they ever heard in the hopes that they might carefully select from their stores of acquired knowledge, the appropriate sentence to give in response. Instead, a new language is learned intuitively by immersion. By reworking error, and re-defining one's grammatic understanding or interpretation of a particular phrase or material implication ect..
Thus one should not commit to memory meaningless facts and solutions to particular problems, instead we learn the broader concepts, and learn to apply them to solve harder and harder problems with expertise. I mean, does one really go about cumbersomely trying to learn a thousand techniques to tackle the infinite number of problems available to him? or does he simply learn only a small number of much simpler concepts from which he may cleverly construct any number of suitable techniques to solve all of the problems available to him?
Well my advice to anyone who is attempting to become proficient in a topic is to constantly redefine and re-invent your strategy and find new ways to better evaluate and consolidate your experience. Try to keep yourself saturated in the core material and constantly work with your deeper intuition. Learn to construct proofs and derivations, have them torn apart and reworked. Develop a rigorous and wholesome exercise regime, use journals ect. to supplement and organise your learning process. Practice proper nutrition and keep to a regular sleeping schedule. Try not to be too hard on yourself. As Dipole has pointed out, forgetting the material is all part of the learning experience. Good luck and don't freak out dude!
Nature uses only the longest threads to weave her patterns, so that each small piece of her fabric reveals the organization of the entire tapestry - Richard Feyman