It has been taught to us by our Rabbis of Blessed Memory that every letter of every word of Torah that we learn creates defending Angels that stand on our Right side and encourage us to do Mitzvos. This is what our Rabbis meant when they taught us "Mitzvah Gerraras Mitzvah" (a Mitzvah causes another Mitzvah).
What happens when we don't learn when we should? Is it really an Aveira? or maybe it's just that we are missing out on a Mitzvah. However, if we miss out on the Mitzvah of Talmud Torah we are also missing all those Melachim (Angels) that we would have created through the letters and words we spoke while we learned. That means that we don't have the influence of all those Melachim upon us to do more Mitzvos.
Our Aveiros can have a stronger influence over us than if we had learned. Therefore, we may tend to do more Aveiros. However, if we actually keep ourselves and others from learning because we spoke of other things when we should have been learning we clearly have done an Aveira. We have stolen the learning and the Mitzvos which the others would have had (besides our own).
Taking away a persons learning is one of the worst Aveiros. As our Rabbis taught us, "Talmud Torah KaNeged Kulam" (learning Torah is the greatest Mitzvah of all). Therefore, stealing away someone -else's Talmud Torah is one of the biggest Aveiros of all. When we sin we create Melachim that influence us to do more sins. Our Rabbis warned us about this when they said, "Aveirah Gerreras Aveirah" (a sin causes us to do another sin).
If we appreciated time we would not waste it doing Aveiros. We would spend all our time doing Mitzvos. Reb Noach Weinberg, Shlita, (Rosh HaYeshiva of Yeshivas Aish HaTorah) often would tell over a story to make this point clear:
There once was a Yeshiva student sitting on a bus. As the bus pulled away from the stop he noticed a man across from throw a five dollar bill out the window. He couldn't believe his eyes.Reb Noach, Shlita, would then say, "Why was the student so sure that the man was crazy? It was because he didn't even appreciate the value of money. What is more valuable five dollars or five minutes? What if those five minutes were the difference between life and death? What if a person could have five more minutes of living? What is worth more five dollars or five minutes of living? The answer is obvious - five minutes of living! But, we don't think twice about wasting our time or the time of others. When we waste time we are wasting our life. We are wasting time for living our lives as B'nei Torah.
Now, who is really being more foolish a person who wastes time or a person who wastes money? Talking when we should be Learning Torah is the worst type of time wasting. That is why it is much worse then the man throwing away his money. Don't be waste time anymore. You have an opportunity to learn Torah, don't throw it out of the window every few minutes.