There is a belief that the third time something is attempted, the likelihood of succeeding is greater than the previous two attempts. It is also used as a good luck charm - spoken just before trying something for the third time. Like a difficult away trip for example.
Two times this season, Atletico Madrid have faced tricky away ties branded as tests which needed to be passed if they wished to prove their title credentials. Two times they have failed those tests, first at Valencia and then at Real Madrid. On Sunday night, they visit Camp Nou.
Luckily for Los Rojiblancos - despite those two defeats - they still remain second and they still remain Barcelona's closest rival. Six points separate the two sides heading into this weekend's fixture, if they wish to cut the gap to three, they may seek encouragement from Real Betis' performance against Barca in Seville last weekend.
They will also have to do something they haven't done since 2006. That was the last time they left Barca's home with maximum points, winning 3-1. They drew a season later, but their five League visits since have seen no joy for Diego Simeone's side. Those five games have an aggregate score of 22-3 for Barcelona, culminating in last season's 5-0 win and Lionel Messi’s hat-trick.
Most surprising about their dire results against La Blaugrana at Camp Nou, is that intertwined with those results are some memorable victories against them at home. Supported by a stellar cast including Sergio Aguero and Diego Forlan, they twice put four past Barca during a run of three straight wins at the Vicente Calderon between 2008 and 2010.
This weekend it has a different feel though. El Cholo has masterminded 12 wins from 15 games this season, including a 100 per cent home record. They are in their best position for years, five points clear of their great city rivals. This weekend, their trip into Catalonia is the main event, the top billing, first vs second.
Regularly rich in South American attackers, this Atleti team is no different. Radamel Falcao smashed five past Deportivo La Coruna last weekend, and the subplot will be him versus Messi. Where this Atleti team does differ though, is in defence. Simeone has established a consistent back four, and they have conceded just 0.86 goals per game in the league this season - Barca average 1.13.
Win, and they will open up the title race not just to themselves, but to Real Madrid too. Some Spanish papers may even rejoice if they lose, and Barcelona would find themselves in a position equivalent to giving Usain Bolt a two second head start over 100m. Uncatchable.
Whether Simeone agrees or not, their defeats at Mestalla and the Santiago Bernabeu were definitely tests, tests of similar ilk to the one that awaits them this weekend. When they step into the lion's den on Sunday night, they will be hoping it is third time lucky.