Other things have triangles too - such as the 'washing up triangle' (not in school text books). Washing the dishes needs 3 things to work well too: soap, heat and friction. If you skimp on one, you need to make it up with the others!
But here's one for what many Christians call our 'devotion life', or 'quiet times' - helpfully crystallised by something Graham Daniels said recently: our devotion life needs 3 things - bible, prayer ... and meditation. (The last is a big theme in the bible, but neglected in our church circles a little. I think it's done, just not talked about much; sounds too hippie.)So in order to build a good personal relationship with the Living God, we need to read our bibles, pray, and think - that's all 'meditation' means.
If we miss out 'bible', it becomes vague Eastern nonsense - just thinking about nothing.
If we miss out 'prayer', it becomes brain-fodder - understanding what God says to us, but not bringing our thoughts and responses back to him.
If we miss out 'meditation', it becomes cold duty - we do our daily bible reading and prayer, but then job done. It's not sunk deep, and we relate no more closely to the Lord.
