The Red Devils were heading towards a first home defeat since the opening day following Didier Drogba's 53rd-minute headed goal, until Robin van Persie struck deep into stoppage time to earn his side a share of the spoils in a 1-1 draw.
"We had a lot of chances but we don't finish these chances, then Chelsea make the first goal and it becomes much more difficult as Chelsea play possession football, make the pitch big and we have to run and run," Van Gaal is quoted as saying by BBC Sport.
"We kept together and I think we deserved it. I have seen that we could have beat Chelsea, I'm saying that nearly every game but this is against Chelsea who are a top team and we were at least equal.
"The most pleasing thing is we are showing again we are believing in making a goal in spite of the result being bad. 1-0 behind it is fantastic the players are running until the 90th minute to equalise or win."
United are now eighth in the Premier League table.