When the season comes to its ending weeks, with very last matches, 3 points in difference are big enough to secure a title. The season in reality still has many remaining matches and 3 points are not too much and not safe for Barcelona to make sure they will lift the league trophy. At least if they can make diference to not only goal difference but point difference with 3 points, it's better.
Barcelona still have best advantage in the title race and they are controlling the race, but Real Madrid won't give up and there are potentiality of rank changes in La Liga. Atletico Madrid have most disadvantage but they won't give up and will fight best first and wait for results of Real Madrid and Barcelona in coming weeks.
When the time comes and we have very few games left, three points will be big enough but at the moment we are not there yet and we can't consider this as a big difference yet. For three points to mean something, there needs to be three games left max, in that case Barcelona could consider, putting their 100% on just three games and get wins, which they could do on their last three games.
But they still have plenty of games left, so they need to focus up and not let any mistakes happen. One mistake and they are behind, so there is no way to relax just yet, they have plenty of times to go. I can see how this could be an issue, they could still lose points, it's impossible they win 100% of their games in my point of view.