The best advice I can give anyone about relationships that already exist is "avoid complacency"
Complacency is the enemy of great love and long relationships and it's so easy to do.
Complacency means you start to trust that the person you are with is yours. My wife, my husband, my partner.
Remind yourself that they are not yours. They stay because it feels right, and because they love you, but if you crap on the lounge that love will soon become second to self preservation.
Crapping on the lounge suite might be extreme, but, getting fat, lazy, using bad language, being disrespectful and in general taking your partner for granted might be the real home of the Devil if there is one.
Hell on earth is when you take your partner for granted, because in doing this, what you are clearly demonstrating is that you think you can take life for granted.
But life can be snuffed in seconds. And all that "taking for granted" can become a regret.
I find that it takes a lot of courage not to fall into the trap of waiting for February 14th in order to remember how important your lover is. You have to admit you need someone in your life. That's vulnerable and possibly not very spiritual according to some texts. But love is need and need is love. It's human and you just need to trust that if you follow your VIP (Vision, Inspiration and Purpose) and never take your partner for granted, complacency will not set in. There's no need to worry.
With Love
Chris