Can stress from work or other situations cause a breakup towards a healthy relationship?

It can, but it doesn't have to. A good, solid, and strong relationship can withstand any trauma, hardship, and stress with out too much damage and destruction. It requires seeing it through TOGETHER...having compassion and understanding, as well as being supportive of each other and not taking your anger and frustrations out on the one you love and is there for you when no one else seems to be. Know your partner... know when to get close as well as when to back away (even leave them alone for awhile). Just keep in mind (and heart) that NOTHING is more important than your relationship, and you will get through it as nothing lasts forever.