How to avoid/deal with being drained?

I still consider myself a beginner, but I’ve gotten confident enough to do readings for others. I recently did a reading for a friend, trying to figure out a way through some family problems she has going on. I organized and cleansed the space, I grounded myself, all of that, and went on with the reading. I ended up channeling a lot of her energy and the energy of the people that are part of the problem, and by the time I was done, I could barely find the strength to stand up on my own. How can I avoid/deal with this?