Editing can make your videos look a lot more polished and professional. YouTube actually has built-in editing tools you can use for free, and you don't need a lot of experience with complicated editing software to be able to use them.
For example, the YouTube Video Editor allows you to trim a video—or basically remove any unnecessary content from the beginning and end. You can also add text to create a title screen and credits. There are even some features you'd usually find in more advanced software, such as video stabilization, an auto-fix feature, and filters to give your videos a stylized effect. Watch these videos from the YouTube Help channel to learn the basics of use the YouTube Video Editor:
If you don't like how the changes turn out, you can always revert back to the original video. Note that it will take a while for your changes to appear on the published version of the video—up to a few hours in some cases. It just depends on the types of edits you're making and the overall length of the video. Still, for simple edits it's hard to beat the convenience of YouTube's built-in editing tools.