Is it rare to loose your vision? i'm so frighteneded of suddenly loosing my vision or something suddenly going wrong

It is rare: Vision is lost suddenly from trauma, vascular catastrophes and some inherited problems. All other causes are slow, give plenty of warning and almost all are treatable. Fear of vision loss is common but if your family is free of this problem and you protect yourself when doing anything which might impact the eyes, then you should have little to worry about.