The former Fulham striker netted the first goal of the second leg on Sunday which saw the Sounders give themselves hope following the Galaxy's 3-0 first leg win in Los Angeles.
The eventual 2-1 win to Seattle was not enough to get them a gig in the 2012 MLS Cup final but Johnson was philosophical despite the disappointment.
"The most painful thing is we're not going to MLS Cup," Johnson said.
"We all cry, we all have feelings, we're all human beings. That hurt today. It still hurts. I'll probably cry some more afterward. There's no success without failure and hopefully we can get it right for next year.
"I think that we always respond when we are facing adversity. We always know how to turn things around, and we couldn't have asked anymore from ourselves. We did everything right tonight."