I couldn't possibly learn a foreign language. I don't have time, I'm hopeless at languages, I've tried before and didn't have much success, and it's just too hard.
These are some of the excuses people use when explaining why they are not studying a foreign language, and if they do actually start learning a language, they often find excuses for putting off their studies, for not practising, for not doing their homework, and so. Such excuses are very common and I've even used a few of them myself.
Taking on something new can be challenging. Even if you're very enthusiastic and determined there will be times when you just don't feel like studying or doing whatever the new thing is. Especially if a lot of work over an extended period of time is required, as is the case with languages. It's great if you study every day, but if you miss a few days here and there there's no need to feel guilty, as long as you don't miss too many. The key is to get into the habit of studying regularly whenever you have some spare time, even if it's only a few minutes.
Excuses can even be turned into a learning exercise - instead of complaining about how hard the language is or your lack of progress in your mother tongue, you could try doing so in the language itself. Maybe you could also make up some interesting, silly, far-fetched or funny excuses for why you haven't studied on a particular day. This would be a way to improve you vocabulary and grammar, and the more bizarre the excuses, the more likely you are to remember the new words and grammatical patterns.
For example, instead of just saying that you didn't study because you were too busy or couldn't be bothered, maybe you could make up a story involving mythical beasts, extraterrestrials, secret missions, or whatever springs to mind.