I remember a time when I was a boy and I climbed a big tree near my house.Of course you remember. When you tell about something that happened to you, you're remembering. Readers understand that; you need not tell them. Just say, When I was a boy, I once climbed a big tree near my house. See? No underbrush to clutter things up. Case two
From these examples, it's easy to see that shoulder harnesses and seat belts save lives.Let the reader decide how easy something is to see. Go straight to the core: These examples demonstrate that shoulder harnesses and seat belts save lives. Or maybe just, Shoulder harnesses and seat belts save lives. Case three
As has already been stated, unforgiveness hurts the person who refuses to forgive at least as much as it does the person who caused the hurt.Readers will recognize when you're restating a concept, and if they don't, then from their perspective, what you're about to say hasn't already been stated. Either way, the opening phrase adds nothing useful. Omit it and begin with unforgiveness. The above three examples all contain material that is peripheral to the topic. It's non-news that requires no explaining, often arising out of an impulse to pad one's writing with filler cliches.