I find that the biggest problem is the vague or impossible goal itself dragging people down before you even get started. Many people phrase their resolution as "Learn Spanish/French/Japanese" without any qualifiers. What does "Learn Chinese" even mean? Learn it to sound like a native? To order food? To write it? And by when?
A language is not an academic topic that you can pass or fail, but a means of communication. There is no "failure" here, just various degrees of success when you can use that language. Do NOT aim for perfection-or-bust. Even a small success of being able to buy lunch in the language, with bad grammar and not using precisely the right word, is something worth being proud of.