What is the meaning of this?

Don't go breaking my heart

I couldn't if I tried

Honey if I get restless

Baby you're not that kind

Don't go breaking my heart

You take the weight off me

Honey when you knocked on my door

I gave you my key

Nobody knows it

When I was down

I was your clown

Nobody knows it

Right from the start

I gave you my heart

I gave you my heart

So don't go breaking my heart

I won't go breaking your heart

Don't go breaking my heart

And nobody told us

'Cause nobody showed us

And now it's up to us babe

I think we can make it

So don't misunderstand me

You put the light in my life

You put the sparks to the flame

I've got your heart in my sights

It means don't break this person's heart as in don't hurt her/him or cheat on her/him.

dont break the persons heat which would mean dont disappoint or hurt the person emotionally, usually used with a relationship