And he told them they should never take their professional football careers for granted as he criticised his side’s second-half display against their Southern League premier south opponents at Fratton Park.
Cowley’s League One side secured a 1-0 win from their first-round Cup clash with the minnows.
Marcus Harness’ sixth goal of the season on 28 minutes separated the two teams, with Harrow proving no pushovers on their visit to PO4.
Cowley praised the Boro players and their manager, Steve Baker, for their display in front of the 6,869 fans in attendance.
But he didn’t feel he could justify throwing similar praise in the direction of his own players after they failed to build on Harness’ opener.
Indeed, despite progressing to the second round of the Cup, he instead felt the need to remind his troops of the fortunate position they find themselves in as professional footballers for a club like Pompey.
Speaking to BBC Solent at the final whistle, Cowley said: ‘I just want to win.
‘I knew how important the game was for us as a club, I knew it was a difficult game and I give massive credit to Steve Baker for his team – I thought they were a credit to themselves and a credit to non-league football.
‘I've managed players at that level, I know how many good players there are at that level.
‘I've worked with Lyle Taylor, Alex Woodyard, Ryan Tafazolli, who have all played in the Championship and who have all played for me in the same tier of football, so I know there's a lot of good players there and Harrow Borough have a lot of good players.
‘I just reminded our players there what a privilege it is to be a professional footballer, how lucky you are to be doing something in a profession you love every day, how much the Harrow Borough players would love to be where you are and to never take it for granted.’
Cowley admitted there was no point in sugar-coating how he felt at the final whistle.
He added the second-half performance was not to the standard he or the club expects.
‘I didn’t like the energy, the intensity or the purpose we played with,’ he said.
‘I'm never going to come out here and lie. I'm always going to stand here and tell you what I think.
‘I've just told the players what I think - and my standards are much, much higher than that.
‘And our standards need to be much, much higher than that if we are going to achieve anything this year.’
When asked how the players responded to his post-match verdict, he added: ‘I wasn't in a debate with them, I just told them’.