What’s the best relationship tip you can give to create and mantain healthy relationship?

Been with my partner for 15 years. My top 2 tips would be

• Honesty. Build a culture in your relationship where you can speak your truth and so can they. It means creating space where they can be heard and they should do the same for you (if they don't, leave).
• make time to 'hangout" together. Doesn't have to be fancy date, just regularly carve out some time to listen to music together, watch a movie and talk about it after, go for a walk...whatever. Connect on stuff that isn't life admin related (bills, kids, chores etc)