Love is a beautiful thing for as long as it last. But it's funny how someone you loved dearly could turn to an enemy you hate so much, it happens.
I'm not exactly an expert but I could try answering your questions,

• How do you manage your relationship: managing one's relationship is about determination first. How determined are you? Are you sure you really want to managed the relationship? Then you go for it. If you're not truly determined, you'd prolly just take the relationship for a ride showing some nonchalant attitude. You manage to relationship by not being selfish, not thinking of yourself only, by communication. Communication I really vital for any relationship. You ask questions too, don't just assume.

*How do you make love a beautiful thing: I think this could be achieved by showing your partner that you care and you're always there for them. Appreciate their little deeds. Be there for them in rough and smooth times and watch how the beauty plays out.

*How do you keep the relationship after the pain and tears: this is where the determination comes in to play again. A relationship with tears and pain isn't a true one. You have to pass through all the stages. But deciding to keep your partner is up to you. You can't just end things because of one fight. If you keep doing that then I guess you'd get tires because I know my gender and I know what we are capable of doing purposely or unpurposely.

*How do you detect if someone's feelings for you is fading gradually:
This hasn't always been a hard part. You'd start noticing some changes. The person no longer wants to be with you as much as before. The person purposely stalls you, avoids you, get angry at little things. The vibe or connection you once had would be fading. You would even be tired at some point because you know that whenever you two are together, there must be a form of disharmony. It gets sickening.

With the little knowledge I have, I guess those are some answers. I hope they answer your questions and clear your doubts.