Padraig Amond's first goal for the Shrimps seven minutes from time earned the home side the points.
Argyle took the lead through a Reuben Reid penalty when Morecambe skipper Mark Hughes was adjudged to have hauled down Marvin Morgan but the home side equalised almost immediately through their talisman Kevin Ellison.
Plymouth went close to taking the lead in the second half before Amond produced a superb finish to volley home the winner seven minutes from time, much to the frustration of Sheridan.
He said: "I thought the game was there for the taking after Morecambe had a hard game in midweek.
"We took the lead and then gave it away about 10 seconds after and that was a massive disappointment.
"I am having to preach into the players the mentality I want because I am not seeing it yet. Some of the lads were blaming the wind for the second half performance but it was the same for both sides and we can't make excuses like that.
"We had a great opportunity here to get something from the game but they believed more than we did and that disappointed me.
"It's all about consistency at this level and we have players who are playing really well one week and then getting nowhere near that level the next and that is something we have to consider."
- Sports & Recreation
- Padraig Amond
- Marvin Morgan