There are hard moments in every relationship. Another thing to consider is whether those "hard complicated" moments happen because maybe you're not with a partner who gives you a healthy relationship. If that's the case, then it's better to walk away from those relationships. If it's just a challenging moment in life, of course, it's best to keep your relationship and support your partner, because life gets complicated all the time, and if in every hard moment people would change their partner, life is going to become miserable and pointless.