Sentence:  I have the right principle and am on the right track, but time, hard work and some good luck are necessary too. It has been just so in all of my inventions. The first step is an intuition, and comes with a burst, then difficulties arise -- this thing gives out and [it is] then that "<WSD>Bugs</WSD>" -- as such little faults and difficulties are called -- show themselves and months of intense watching, study and labor are requisite before commercial success or failure is certainly reached. 
Meaning of the word marked with <WSD> tags:  (Q179550)  A problem that needs fixing.