But Di Matteo said: "Nothing has been achieved. Nothing has changed from last week.
"We have got another game coming up on Wednesday (against Coventry) and it is important that we do well again because the teams behind us keep picking up points as well.
"We are in a good position but as you know, you can lose it very quickly in football.
"It was important to get three points against Preston as we need to do well in our home games."
Albion made the perfect start when Ben Watson and Chris Brunt powered them into a 2-0 lead after just nine minutes.
Sean St Ledger handed Preston a lifeline six minutes later only for Graham Dorrans to restore Albion's two-goal advantage with a 30-yard free-kick.
Neil Mellor then fired Preston back into the game again two minutes before half-time but an equaliser proved to be beyond them.
While pleased with his side's goal threat, Di Matteo admits they need to tighten up at the back having conceded 42 goals so far this season.
He added: "I am disappointed with the two goals we conceded as they are mistakes we shouldn't be making.
"Defensively we need to do better, there is no question about that.
"But on the other hand we have had to change the back four quite often and that doesn't help. It is about finding a balance where you are solid but you don't lose too much going forward.
"I would like to keep more clean sheets and be more solid."
Di Matteo shrugged off the mixed reception strike Luke Moore got from some of the Albion fans when he replaced Ishmael Miller in the 72nd minute.
"It is a bit bizarre that you boo one of your own players," admitted Di Matteo.
"But I would emphasise it is a minority."
Albion's win ended Preston's five-match unbeaten run but North End boss Darren Ferguson was full of praise for his side's tenacious display - although he was disappointed with the goals they conceded.
Ferguson said: "We conceded two poor goals and gave ourselves a mountain to climb.
"They were sloppy goals but we dug in and kept going and West Brom will
know they have been in a game.
"We weren't far off them and they do look like a team who will be in the Premier League next season. We had some sustained pressure but the goals we are conceding are costing us points.
"But it was our first defeat in six and we have to get ready to go again on Tuesday (against Middlesbrough) in another big game."
The defeat has all but extinguished Preston's lingering play-off hopes and Ferguson added: "Anyone who goes on a run has got a chance. But I think too many draws will probably cost us."