When you lose something, it's an unintended, often unexpected event. It usually involves some level of frustration or sadness, as you can't find the item and didn't mean to part with it. For example, losing your keys or wallet.
On the other hand, getting rid of something is a deliberate action. It means you intentionally decide to dispose of or remove the item from your life, often because it's no longer useful or needed. For example, decluttering your closet and donating old clothes.
In short, losing something is accidental, while getting rid of something is intentional.