Aadmi kaa agar iraadaa pakkaa ho to darwaaze to khud ba khud khul jaate hain

Film : Duniya
Year of release : 1984
Spoken by : Mohan Kumar (Dilip Kumar)
Spoken to : Balwant (Amrish Puri)

This revenge drama has Mohan breaking into Balwant's house. Balwant asks him the silly but inevitable question

"Tum andar kaise aaye"

And Mr Mohan Kumar says

"Aadmi kaa iraadaa pakkaa ho to darwaaze to khud ba khud khul jaate haiN"

"आदमी का इरादा पक्का हो तो दरवाज़े तो ख़ुद ब ख़ुद खुल जाते हैं"

A thought echoed, in a slightly romantic fashion, by Shri Shahrukh Khan in his Om Shanti Om, when he says

"इतनी शिद्दत से मैने तुम्हे पाने की कोशिश की है, कि हर ज़र्रे ने तुम्हे मुझसे मिलाने की साज़िश की है"

Personally, I too feel that if one really wants to do something, he generally does it. Simple line, but interesting usage. So you can use this line, when you break into someone's house.