But Zebre could have been in front had they not missed four kicks in the opening 46 minutes and, even after the Welsh side went ahead, the GUINNESS PRO12's bottom team twice knocked on with the opposition defence retreating.
Guidi said: "We missed two simple situations that have cost 14 points and maybe now we would be talking about something else.
"We have to be so angry about this great opportunity which was lost. We are here to win games; the honourable defeats do not interest me."
Sunday was fly-half Edoardo Padovani's first game of the season and he endured a difficult afternoon at the Stadio Sergio Lanfranchi.
The Italian missed three penalties and a conversion before being replaced by Ian McKinley after just 46 minutes.
But Guidi said: "On Padovani, it must be said that it was his first game in four months and he also did many other good things for which he should be acknowledged.
"We must also give him time to grow because he is only 22 years old. His performance is a good omen for the future."
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