Stress in optimized amount can help in increasing the memory but if the stress is more or extreme then we may experience short term memory loss.
Step-by-step explanation:
The stress causes the release of stress hormones which will color the memory based on our stress perspective. So if we are stressed while learning something new our brain finds it difficult to store the learning as long term memory due to stress hormones.
But if we got stress after storage of memory then it will help to retrieve the memory as the stress will be acting as the retrieving agent in such cases.