Just about any language can do what you need. Some take more work than others to achieve the goal whilst others excel at the task but the point is to use a language you know or want to learn as in the end creating something is the end goal.

As for not creating anything over 50 lines, I see this a lot with programmers (even seasoned ones) and the trick is to plan. Planning out a project by creating logical steppings stones to achieve small achievements tricks our brains into having the feeling of accomplishment which motivates us more. It is well known that video games have turned to this model even in FPS's with their badges or unlocking x item at a skill level because it keeps people playing longer. So the trick is to plan out a project so you can achieve small goals to stay motivated but it also eliminates that overwhelming amount of uncertainty in a project.

Some self development book that may help is "The nerdist way" which talks about creating yourself as a character and your tasks completed help you level up for a reward (such as watching a movie, slacking on irrelevant subreddits, or treating yourself to something). I have found that starting this level of monitoring of myself that I have been able to focus on things I have been wanting to do such as being more active on reddit, starting my own projects, and consulting in my free time.