A stationary wave is formed by the superposition of two waves with the same frequency and amplitude travelling at the same speed in opposite direction.
Consider a wave generated by a vibrator is travelling to the right and approaching a fixed end.
The wave is then reflected at the fixed end.
The reflected wave is travelling to the left while the incident wave is travelling to the right.
Why the reflected wave from the right is not reflected again at the left when it arrives to the position of the vibrator? If it does, shouldn't there be two waves travelling to the right after the second reflection and hence amplitude of the stationary wave should increase along with time? If it doesn't, where will be the reflection wave?