[Sweet creature
Had another talk about where it's going wrong
But we're still young
We don't know where we're going
But we know where we belong]

The two in the relationship are still very young and uninformed, hence the line 'we don't know where we're going.' However, they know that they want to be together, and they're obviously very fond of eachother as they have chosen to talk about where it's going wrong instead of just ending it.

[Oh, we started
Two hearts in one home
It's hard when we argue
We're both stubborn
I know, but oh]

Two hearts in one home - the couple may live together, or they may be referring to their relationship as this 'home' in which they both find refuge. They acknowledge that they both have undesirable attributes - ie. being stubborn - but work with it nonetheless.

[Sweet creature, sweet creature
Wherever I go, you bring me home
Sweet creature, sweet creature
When I run out of road, you bring me home]

The use of the term 'sweet creature' implies there is a bittersweet sense to their relationship. The person is loving, but perhaps the strong feelings they cause the writer to feel are unfamiliar, hence the reference to the person as a 'creature'. However, he acknowledges anyway that the person brings him back down to Earth.

[Sweet creature
We're running through the garden
Oh, where nothing bothered us
But we're still young
I always think about you and how we don't speak enough]

writer perhaps does not live with the person anymore, does not see them as often as in previous years. Again he is acknowledging that they are still young, but he's beginning to realise things are better when he is with that person.