That sounds like a healthy approach - relying on your sister!
I read somewhere that the happiest people make a practice of "sweetening their memories." They constantly recall positive things they did and reflect on what was great about them.
One of the dangers of journal writing is we tend to do it when we're depressed or anxious. Maybe it's great as a tool for working out negative emotions, but at the same time it's making them more concrete in the memory. That's why I don't often like to go back through my old ones. I think, ugh, I'd forgotten that dreadful thing happened.
I was a terror as a sister, I can't even believe some of the things my sister told me (I am the eldest). Luckily she also remembers me threatening (her) bullies so badly in primary school they never even looked at her again. Ah, redemption!
Good for you! You're the sort of woman I want on my side!