As a ScrumMaster when you are “running” a retrospective it is easy to fall into the trap of actively participating in it. It is extremely difficult to do this well (if not impossible), because your role should be as a facilitator not a participant. The minute you start participating you are no longer neutral and severely impact your ability to effectively facilitate.
Sometimes the need to take advantage of coaching moment or provide input is too great. One way to handle this is let the group know you are taking your facilitator hat off for a moment and acting as a coach or a participant to briefly add the input and then put your facilitator hat back on. This should be used sparingly and know that it will greatly affect your ability to be seen as neutral. However, it will at least signal to the participants your understanding that a facilitator should not be a participant. Clear boundaries are good.
A way to prevent frustration (and burn out) is to not be the one always facilitating the retrospective. Ask another scrum master to switch it up with you. Ask a team member if they want a turn. They might just surprise you.