Cosgrove's persistence paid off early in the 1-1 draw against Crewe on Saturday, as a kind bounce from a rebound off goalkeeper Will Jaaskelainen saw the striker convert at the second attempt.
It was the on-loan Birmingham frontman's second goal in two home league games and the Town boss said he was not interested in how it went in, instead the move involved in the build-up.
"The goal was all about the run. I don't care how it's gone in, it's all about that run," Cotterill said after Cosgrove finished a neat move involving Josh Vela and Luke Leahy.
"Those are the things we've been working on, making that run, the fact he made first contact, it looked like it was saved and came back off him and went in.
"It doesn't matter, I'm sure that while Sam's here he'll take 15 or 20 of those, but the reason he got that is all about the run, that's what makes the goal."
Cotterill, who brought Cosgrove off after the hour, admits the rangy striker has plenty left to work on following his late window loan from Blues.
He added: "Yes (strikers are confidence players) – and they will tell you they are not.
"Everything is on confidence. If they haven't scored for three games, it'll be written about and the young lads will read it, and they'll already know they haven't scored for three or four games.
"There's some gains from Sam from Saturday, and there's also some stuff we need to work on with him.
"One of those will be – like the other boys who came in (signed) later – he's behind with regards to fitness. All of those boys who missed part of pre-season are behind the others."
Cotterill was so impressed with Vela's through ball to the byline for Leahy he appeared to celebrate the pass before Cosgrove's finish. The boss added: "It's because I said we'd score from it. I was (celebrating it) because it's a pass we'd worked on.
"Once we get in those areas, we do outside-inside touches and passes, we're then putting the opposition into a real corridor they don't want to be in.
"And then the runs are important, once we got in there I knew we could score, I saw how many we had in the box and thought if we get this pass right we'll score."
"Those are small things that you need to fall for you on any God given day, we've been working on those things.
"The distances and execution was right, the right weight of pass, the cross was right and the run was right. All we'd worked on came into that goal, which was really pleasing."