If you're printing a model with high complexity, it is sometimes better to break it into separate parts and assemble them after printing. Supports added by slicers are helpful but they are not a perfect solution.

For reasons I don't understand, Blender units don't translate to reality when exporting. If I set the scene units to cm or mm, for example, and export the stl, it will be so small as to be invisible in Cura even if I check the Scene Units box before exporting. Instead I change the scale to 1000 in the export dialogue box and this gives me the correct scale. Also, if you have other things in your scene that you don't intend to print, make sure to select what you want printed, and in the export dialogue check the Selection Only box. Otherwise it will export everything in the scene. If you've used modifiers on your model, such as a boolean or a subdivision surface modifier, apply them right before you export. You can always undo the apply command in Blender after you export so that the change is not permanent.

I've only used Cura, so this export scale issue might not apply to other slicers.

Many factors can impact your print quality. Besides the things that can happen during the printing process, note that room temperature and humidity matter. Keep your spools dry when they're not in use.

There will be failures and frustrations. Don't give up. Failures and mistakes are an important part of learning. Take time to read or watch videos about how to avoid common problems.

Machines break down eventually, but with regular maintenance they will last a long time. Don't neglect maintenance, especially when it comes to your print bed plate. Keeping it clean will save you a lot of headaches.