Kevin Dawson netted the only goal before the break and Johnson admitted: "I am very happy with that performance, we played some very good football and looked very solid.
"We gave six or so players who didn't play in the opening league game a run out and I was pleased with that.
"We probably needed the second goal so it didn't seem so nervy but the boys at the back did their job very well restricting Southend to very few chances.
"That meant we came out worthy winners and I was enthused by a lot of our play.
"Some of the new lads have shown superb fitness and game mentality and a credit to everyone at the club for that.
"Kevin Dawson popped up with the goal and he is proving to be a great signing for us.
"He took his goal excellently and is showing what sort of player he is going to be this season."
Southend boss Phil Brown added: "I thought we had the performance but not the result but I'm relatively pleased with our performance.
"Yeovil showed their Championship quality at times which did make a difference but our desire and will to win was certainly there and we got more in to it the longer the game went on.
"We could have snatched an equaliser at the end and maybe we didn't deserve to lose."