Is the man you love acting like a ghost in your relationship? Maybe he's even vocalized that he needs space? Perhaps he claims nothing's wrong, but he just doesn't return your texts and seems to be a whole lot busier than he was in the early stages of dating?
Before you convince yourself that he has one foot out of the relationship, ask yourself if you truly believe that he is capable of commitment and a long-term partnership. Also ask yourself if you feel, on a gut level, that he truly loves you and wants a relationship with you. If you feel confident that he is an emotionally available man and is in love with you, then this space could be a good thing. If you feel doubtful that he has the ability to love, then it is time to say goodbye.

When a man pulls back or carries on like he needs space, it can mean that he is in fact so serious about the relationship that he needs time to assess his feelings and decide whether the relationship is healthy for him long-term. Men are more in their heads than women and when the thunderbolt of love hits them, they may need to take a step back and look at things more logically.

The key for you is to handle his need for space in a way that's respectful and dignified. It's okay to communicate your feelings (like in a letter) or to ask him questions about what he's thinking. But don't smother him and don't make him feel guilty and accused.

This doesn't mean you have to ignore your feelings when he needs space. It's important to honor your feelings and to not reward behavior that hurts you by being too flexible.