Saints suffered a 1-0 defeat by Livingston in the Betfred Cup semi-finals at Hampden and were moments away from securing a Scottish Premiership top-six place before conceding an equaliser at Hamilton.
They have the chance to embark on another journey when they return to Lanarkshire to face Accies in the third round of the Scottish Cup on Saturday.
"Not achieving top six, we have had to re-evaluate our ambitions this season, and going on a good cup run is the next target," McCarthy said.
"When we found out the cup was being played we were delighted, because it gives us the chance for silverware. We don't want the league to fizzle out or trudge on, we want to play for something, and hopefully that can be the Scottish Cup.
"We have proved a lot of people wrong this season and I see it day in day out the quality of players we have at the manager's disposal. So I do think we have got what it takes to go all the way in the Scottish Cup.
"Having been to Hampden already this season, there's no reason we can't get there.
"It really drives us as players, the carrot is there for us to play in such a fantastic stadium. Fingers-crossed we start the road to Hampden this weekend."
The former Cork City player is driven to taste more success after major achievements earlier in his career.
"I won a League of Ireland and two FAI Cups," the 22-year-old said.
"Any player you speak to will tell you that, once you win one, then you want the next one. That's what drives you on. There is no feeling like it, playing on the big stage and winning some silverware."