Development Schedule – No standard rules or measure to apply

While I observe that most developers breaking their head against the code, working late night and getting exhausted till the delivary time arrives, some teams are working in relaxed mode and they never miss schedule. They always deliver on time and are in very good relation with client and so on…

What can be the secret behind this…
– Uneducated client
– Smart Delivary/Project Manager
– Expert developers
– Excellent Scoping exercise
– smartly created schedule..

All DMs and PMs are always starving for the same I explained above…then..
OR
Simply LUCK ..?