You also need to consider the bigger picture too guys, as I explained in a similar post earlier. You need to at least somewhat aware of the mechanics involved. Working with any type of magical objective you need to have at least a good level of understanding on mechanical attributes such as;
The path of least resistance
These are some of the mechanics involved when casting a spell, and I agree with you there on your point about doubting your spell, you have to be very sure of the attributes mentioned above, because the last thing you want is your spell to bounce back and hit you!
And you totally nailed it about time dude, placing emphasis on the fact that if you spend more time working through the problem, and finding a solution your own way, it places a certain connectedness to yourself thus empowering you to perform your spell better.