The 19-year-old returned to Spurs Lodge on Monday for pre-season training after taking part in the World Under-20 Championship in Holland last month.
Reto's Switzerland squad were highly-fancied going into the tournament but surprisingly crashed out at the group stage.
Things started well with a 2-1 win against South Korea - Reto set up both goals - but the Swiss then lost 1-0 against Brazil before crumbling to a 3-0 defeat against Nigeria.
"We played well in the first game and it went okay for me as well, I made two assists but we had a game every three days and for some players it was too much.
"In the second game against Brazil we played well, had a lot of opportunities but didn't score. Then against Nigeria was no good for us, we lost 3-0.
"South Korea were technically very good and had lots of fighting spirit, Brazil are also technically very good but we were physically stronger and Nigeria was the most difficult, they were strong and that was hard for us.
"I think we had the hardest group in the tournament and I actually think we played well but we needed the goals at key moment to get through the group. That's football and we have to accept that. It was still a great experience for me."
With senior Swiss internationals at the end of May and the World Championship in mid-June, Reto managed to squeeze in two two-week breaks as his summer rest.
He was his bubbly self back at the Lodge. "I feel good and I'm excited by the prospect of playing football again," he added. "I feel relaxed, I've had a good time with my family and girlfriend and I now have a lot of energy for the next season.
"I've been running again and I feel okay. I'm not quite ready for the tournament in South Korea because we have three games in six days so I will stay here and get fit."
Reto Ziegler is ready to put his World Championship woe behind him and is raring to go for the new season.