Anthony Gordon's first-half strike was enough for the visitors to win 1-0 at Stamford Bridge.
Howe said: "That was such an important victory with what we have coming up ahead this week with the two massive games."
Ahead of their Champions League round 16 second-leg at Barcelona, Howe also said: "It is great to go into these games with the good feeling that we have. And I thought the mentality, the effort today was very, very good. You mentioned the mentality and effort.
“Yeah, it gives us huge belief. I think we needed to win today to give us any chance of winning in Barcelona and progressing through the Champions League. It's such a difficult game, but you need that confidence that winning gives you."
Sandro Tonali missed the win, though Howe has hoped he will be fit for the trip to Spain.
"He was feeling unwell after training yesterday. It quickly became apparent that he would not be able to travel.
"Fingers crossed it follows a similar pattern with the other illnesses we've had and it is a quick recovery. There has been something going around now for two or three weeks in the squad and hopefully this is the same."