If your main character doesn't have conflict and obstacles to overcome, then your story probably isn't complete. In life, things get hard. The going gets tough. Enemies appear. I want to see that in your book...and then, I want to see the main character defeat them. This is why your main character is also known as the hero.
Nobody Said Life Was Fair
Here's the thing: you want readers to identify with your main character. Nobody's life is just perfectly smooth sailing. We all get crushes on people who don't like us back, spill something on ourselves at the worst possible time, get caught in the rain or in an embarrassing situation. Some people face extreme challenges, and often these make for the best stories.
If your character faces no obstacles and lives a life free of conflict, I'm not going to find it believable. Even worse, I'm probably not going to like this character. Conflict and obstacles are an essential part of every plot. You don't necessarily have to have a villain, a character in the story who opposes your hero, but you do have to have something that keeps us from our goal. If the character is trying to solve a crime, put a nosy so-and-so in the way. If the character is trying to be prom queen, put an opponent into the mix. Or, mix it up and don't use a character at all. Maybe something happens to the main character with no outside help -- the hero falls and breaks a bone, and now they're physically limited. Conflict comes in many forms, and writing is a great way to explore it.
Everyone faces challenges, and your main character should have the same experience. It's most rewarding to readers when the hero overcomes those challenges in order to get to their ultimate goal. Removing these obstacles shouldn't be neat and easy, because life so rarely is. Perhaps it's a story about a girl who's in love with a boy, buy he's got a girlfriend already. She's an obstacle. The more difficult she is to remove, the more rewarding it's going to be when she's finally out of the way. The struggle is the story, and that's what great writing is all about.
You've already got everything you need to write about conflict and obstacles when you're writing fiction. As a writer, you've already faced all sorts of challenges in picking the right words, in facing your own fears, in finding courage and even in facing down those who oppose you. Now, go write about it.