Foster, who took charge of the Middle Road outfit on Christmas Eve, guided Mussels to a surprise 1-0 triumph at SCFL Premier Division high-fliers Horsham YMCA in his opening match.
Thomas Johnston's 75th-minute effort proved the difference to fire Shoreham to just a fifth league win of the season.
And new boss Foster was impressed with what he saw from Mussels.
"It was amazing to get off to such a good start," Foster said.
"Against an extremely talented side, it was always going to be difficult.
"I just wanted my players to believe in themselves and the way we want them to set up. They did it and executed our game plan perfectly.
"It’s been a frustrating time for some of them and they deserved to enjoy every minute of the win."
Mussels go in search of successive victories for the first time since October when they welcome AFC Uckfield Town tomorrow (7.45pm).
But Foster is refusing to get too carried away after such a positive start to life as Shoreham manager.
He added: "Everyone is now focused for Tuesday. There is no easy game in this league and if you aren’t switched on you’ll get punished.
There is no pressure on the players to win games. But there is an expectancy that they believe they can."
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