"After what happened last week at Leeds, and with our international players coming back after Six Nations duty, we had to concentrate on what we do well and start well," said Johnson.
"Our emphasis was on the first ten minutes and Lewis Moody gave is the start we needed with that catch from the kick-off.
"Last week I felt like retiring. After this win and this fantastic occasion I feel like playing on for ever.
"It was great to come back to Lansdowne Road again and be part of a fantastic Heineken Cup quarter-final weekend.
"It's just amazing just how far this tournament has come. We had more fans at Lansdowne road that we had in our first final back in 1997.
"We snuck into the quarter-finals from the Pool Stages and we took our chance today. We scored tries at crucial times in both halves and im really proud of the way the guys played.
"Toulouse in the semi-final will be another huge challenge, but this Leicester side always rises to a challenge.
"We played better today then we have done for months - we really raised ourselves.
"Toulouse are really the quality team in the tournament, they have such a strong squad and they put Northampton away fairly comfortably.
"But they are the sort of team you have to beat to get to the final.