I think often when our Brain is going through a lot of stress,
whether that is through life events, or starting a new drug,
it protects itself by shutting down some of the memory storage areas
so that it can use its energy on keeping vital life saving areas of our body working.
Starting a new drug can be quite a traumatic experience.
Our brain is receiving a direct chemical attack.
So it makes sence that it would protect itself.
As our minds and bodies get used to the drug then we should be able to re-activate those 'storage areas'.
However I think we have to be active in making this happen.
When you are feeling a little better spend some time reading your diaries, and looking in photo albums. It will help get things moving again.
Of course this is just my theory, but it seems to work for me