This is an area that I study - and the linked article has it right. Constantly testing your new knowledge is the best known way to remember things long term. And this is generally true for all people - we're all individuals, yadda yadda, but we all have human minds (I think! I sometimes wonder) which function in similar ways. Also: Age related cognitive decline is a real thing, youngsters. We weren't born this forgetful, we earned it and so will you if you're lucky. And we don't "only use 10% of our minds" or other silliness. We are really just not as smart as we think. If you have trouble memorizing lyrics or solos, practicing them without notes is the best way to learn. Another proven technique from language learning is to try memorizing long strings of information - such as the pronunciation of complex new words or phrases - by first memorizing the end bit, then adding chunks from there, gradually working towards the beginning bit. So you might start with the last four bars of a solo, nail that, then add the 4 previous bars, etc.