Goals in either half from Tom Adeyemi and Marcello Trotta were enough for the Bees to record their first success in eight and Smith admitted those strikes were key.
He said: "We got in their box but couldn't execute. They got in ours and they did simple as that."
Smith defended the controversial decision to drop Mark Roberts for the first time in his three-year Stevenage career, insisting he wanted fresher legs to combat Brentford.
"The bottom line is that is not an issue. The difference was that you have to hit the target to win games and we didn't do that," he said.
"We are at a stage now where you begin to look over your shoulder but we have a strong competitive unit here and they are all working full tilt to turn it round."
- Sports & Recreation
- Tom Adeyemi
- Marcello Trotta