So just what is an intelligent process to making these tough decisions? A fair plan is one that is truly progressive and gradual. It should take the simplest and most positive approach first. This would most likely begin by sitting down and discussing the situation, how each person feels, what each most needs and needs to have changed, what each honestly wants from the relationship, and what each feels is missing.
If you're in a relationship where you just can't seem to coexist peacefully, there are several crucial things to keep in mind, here. Rather than turning this into an argument or bashing session, you should promise to talk calmly and deal with things reasonably. Instead of using statements like "you are so..." or "you don't..." start with I-statements. Tell your partner things such as, "I need you to be more..." or "I feel as if we..."
Next, discuss what changes you each can and are willing to try to improve things. If both partners feel it's worth the chance (and there are few situations that absolutely wouldn't), make a joint effort to get along better and honor those promises. Both must give a little (or a lot) in order for any positive changes to occur. Just as the cliche notes, it does take two. One partner can't mend a relationship alone, and shouldn't be expected to. Vow to give this a sincere effort for a given amount of time, say a month or so. Then, come back and share how you both feel things are.