Relax and the answers will come. I remember reading this once.
If you have an idea or though that escapes you and you try really hard that it does not come back. Try some arbitrary activity that can completely take your mind off it and you will be surprised how likely it is that it will come back to you.
Try reading, watching tv, a conversation with a friend on an unrelated topic.
If you also can’t remember something, try working your way through the alphabet, this is a technique particularly treated to name, people and places e.t.c.