Okay, I understand and thanks a lot. This will definitely help me in my writing especially understanding this blasted thesaurus.Tip: It's not how you say things; it's what you say. Sure, part of telling a good story is doing it in a way that grips a reader, but fic quality isn't always increased by word variety unless you've got a lot of repetition going on. Repetition, meanwhile, isn't necessarily solved by replacing single words. If you're encountering a lot of repetition issues, you may actually need an entire rephrasing instead -- as in, restructuring a paragraph or an image in order to go at details from a different angle or simplifying what you're saying to merge descriptions into one block. For example, if you're describing Jane going to the store, you'd cut out a lot of repetition by describing her opening the door only once. Some writers -- especially new ones -- sometimes feel the need to describe the door in heavy detail, and in doing so, they end up mentioning that she's leaving more than once. Simplifying your narration = boiling down your paragraphs to only what you need to convey.
That being said, Quilava's got the basic point, but let me expand by explaining what I passed to him. It's okay to use different words, especially if you have no choice but to use similar words in a sentence or paragraph. The trick is that you never want to use words you aren't completely familiar with. That sounds like exactly what Quilava was saying, but what I mean is use a dictionary, not a thesaurus. Thesauri are great jumping-off points, but new writers get in the habit of using only them. Unfortunately, thesauri do two things that can trip you up. First, they usually give you approximate synonyms (words that technically mean the same thing or roughly the same thing but don't actually carry the same meaning in context, like the words "whispered" and "mumbled"), rather than exact synonyms. Second, they never tell you what each synonym actually means. If you find a word via the thesaurus, look it up and familiarize yourself with its meaning. Google it to find out how people use it in a sentence. Don't use it until you know exactly how it works. Otherwise, yeah, you'll end up using it awkwardly.
And it doesn't even really take that much effort, either. Most of the time, you can find both synonyms and definitions via quick Google searches. Typing in "synonym" and whatever word you're trying to replace via Google yields you plenty of online thesauri, "define: [insert word here]" written into a Google search bar turns the engine into a dictionary, and, well, Googling the word by itself gets you examples. With a fast enough internet connection, you'll have a word, its definition, and how it's used in a sentence in under a minute. Yes, it's extra work, but hey, you're a writer. Writing isn't always just about sitting down and having your fingers cough up words. (Weird analogy, I know.)
To answer the question directly, most of what I struggle with is finding the time and energy to write. My biggest fic is on an ongoing hiatus that started in August (not including chapter edits) because I just couldn't push myself to write more. Either I was working on a project for school until I passed out, or I spent all day running around until I passed out. When I did get a day off, all I'd really want to do is lie around and do nothing, and even then, I was thinking about something else. I'm hoping this year, I can train myself to have decent time management skills, but... *shrug*
Then there's the lack of motivation brought on by a lack of confidence in my own writing, but eh, everyone gets that.
And also, there's my habit of being repetitive at times. I can point it out in others' work, but sometimes, I proofread too quickly to catch it myself. Oops. (Hey, that's what a beta is for anyway, right?)