2. Don’t expect them to take your advice.
They probably won’t. Just because you give them advice does not mean it is the right advice for them or that it’s anything they will listen to. Often when people are struggling, they don’t know what to do and hearing different opinions only exacerbates the confusion. They need to work it out for themselves, but it is still important that they have your opinion (if it’s welcomed).
If you wait for them to change and to finally take on everything you’ve given them and told them, it’s going to be a long wait. And a painful one at that. You will become invested more than you ever should. Your life will slowly stop being yours and suddenly become theirs, and every thing that happens in their life that goes further away from your advice, the more it hurts. It’s complicated, it’s frustrating, but it’s not worth risking your own mental health over.