The key to learning a new language is to understand its data structures. Thats a hack i use when i try to learn a new language, since data structures (arrays, hashes, array of arrays, hashes of arrays, trees) are different in every programming language and you get a taste for how the language is moulded in order for the programmer to be effective in a particular area of technical implementation, for which the programming language is originally intended.
One can get too comfortable with a programming language and its data structures too and use it to demonstrate the solution to a complex problem (say like a chess engine ) but at the point of scale and performance you can realise its not such a good idea after all.
There is also the matter of 'expressivity'. A Programming Language holds within it the power of technical expression, and you can use it to express a technical solution to various problems the industry faces, and hence your comfort level with a new programming language has to do with how well you can use it to express the problem you are facing.
Way back in 2002, as an unemployed techie beginner i had to learn Java on my own to get a job, and having been used to Perl i found it wierd you have to write five lines of code just to say hello world.
But when i got my first high paying job as an Enterprise Application developer, and worked in a 30 member developer team building an insurance contract engine using Java/J2EE , i realised how important a programming language Java was when it comes to building practical , resilient and performant engines that drive various industry like Insurance and Healthcare.
All the best for your programming language learning experiences.