But this assumes that whatever you give when you love someone is limited or scarce, so that giving some (or more) to Jane or Joe means giving less to Janet or John.
Will this "sometime thing" truly make him or her happy?
This is reminiscient of what I wrote in my post regarding inadequacy: it's one thing to respect the other person's choice, but it's another to hang too much weight on that when you feel it's not the best choice for him or her.
Do you really want this person you love—more than your committed partner—to settle for second place, in your day-to-day life if not your heart?
This is tough—how often do we find true love in the first place?
Another possibility is that your partner is no longer emotionally committed to the relationship, which is maintained for other reasons, such as children, finances, cultural or religious factors, and so forth.
And understandably, it may be difficult for you to stay emotionally committed to this relationship also, which may leave a void within you that needs to be filled with a new love.
If your partner values exclusivity and monogamy, you are cheating him or her out of an aspect of your relationship that your partner holds dear, whether he or she is aware of the other relationship or not.
(And if your partner is not aware of the other relationship, then you've brought deception into the mix, either through silence, hiding, and sneaking around, or by outright lying.) Of course, your significant other may not value monogamy, in which case presumably you can be open about your other relationship.
Sometimes you can't leave, or other times you don't Another thought provoking post!