This is probably a goodbye song to a loved one (most likely girlfriend) because he needs some time to himself.
I think in the first verse he's talking about how he left her maybe because he is trying to find himself. Being in a relationship is too much to ask at this time in his life when he should focus on himself. He can't guarantee he'll speak to her because he doesn't know where life will take him, but if there was a better situation where he could be himself with her ('For that moment I was never what I am' ) then he would take it. But there isn't, so he leaves to travel.
'I won't forget' and 'If you think of me, I will think of you' shows he could go back to the relationship after this break because it was something worth having.
Verse 2 for me is him stating what was wrong with her and why he had to leave. 'In between the lines is the only place you'll find what you're missing but you didn't know was there' implies that she is someone who doesn't see or read between the lines; she is just seeing the obvious and getting by without curiosity. He wants to do this opposite to this.
The whole chorus I think says that if after this break they get back together again or after he returns home and the relationship carries on as before, she could go and travel as well. In the last chorus he also suggests that 'maybe sometime in a long time you'll remember what I had said there I said I'll be home for next year, darling' referring to what he said when he left her just then.
That could all be completely wrong, but it's how I interpreted it :)
This is probably a goodbye song to a loved one (most likely girlfriend) because he needs some time to himself. I think in the first verse he's talking about how he left her maybe because he is trying to find himself. Being in a relationship is too much to ask at this time in his life when he should focus on himself. He can't guarantee he'll speak to her because he doesn't know where life will take him, but if there was a better situation where he could be himself with her ('For that moment I was never what I am' ) then he would take it. But there isn't, so he leaves to travel. 'I won't forget' and 'If you think of me, I will think of you' shows he could go back to the relationship after this break because it was something worth having. Verse 2 for me is him stating what was wrong with her and why he had to leave. 'In between the lines is the only place you'll find what you're missing but you didn't know was there' implies that she is someone who doesn't see or read between the lines; she is just seeing the obvious and getting by without curiosity. He wants to do this opposite to this. The whole chorus I think says that if after this break they get back together again or after he returns home and the relationship carries on as before, she could go and travel as well. In the last chorus he also suggests that 'maybe sometime in a long time you'll remember what I had said there I said I'll be home for next year, darling' referring to what he said when he left her just then. That could all be completely wrong, but it's how I interpreted it :)