And Moshe spoke accordingly (about redemption) to the Children of Israel, but they did not listen to Moshe because of their shortness of breath and from the hard work (6:9)
The Seforno tells us that the Jewish People, by refusing to allow themselves to believe that they were about to be redeemed squandered a unique opportunity, and as a result, only their children — and not them — would merit entering Eretz Yisroel. The Seforno also notes that they were not able to think of their redemption due to the heavy labor which mentally and physically took up their lives. If the Jewish People were genuinely not capable of contemplating what Moshe was saying to them due to their troubled lives, why were they punished?
The answer can be found in the Paneach Raza who explains that there was something deeper to their rejection of Moshe’s prophecy. He explains that more than their present difficulties, they feared that if they took the step to believe that Hashem was about to redeem them, it meant that they would have to accept the “burden” of receiving the Torah, which they felt was too great for them. Essentially, they feared that they were not on the spiritual level to serve Hashem! As such, they preferred to stay in Egypt and suffer their fate.
On this answer, too, we can ask the same question: if the Jewish People did not feel that they were on a sufficient spiritual level to serve Hashem, why were they punished; perhaps they were right?
The answer must be that Hashem never expects from us more than we are capable to doing. As such, their entire claim had no weight and their real reason for rejecting Moshe’s words was in order to avoid the yoke of the Torah and it’s mitzvos.
There are times in our lives, too, when we turn away from opportunities to grow in our religiousness for fear that we will be stretched out of our comfort zone. Even those who are “fully religious” often get to a point where they are comfortable with their level and reject further growth. The joke that “anyone less than my level of religiousness is barely Jewish and anyone above my level is a fanatic!” more often than not, rings true to our ears. However, we see from the Torah’s message that closing our eyes to opportunities of growth forms a baseless claim and is simply an excuse to continue our lives in a way that suits us.
One unfortunate example of this was often related by Rav Noach Weinberg after he gave a class to secular Jews demonstrating compelling evidence of the existence to Hashem and the validity of the Torah. It became noticeable that one person in particular was really getting into it. But, towards the climax of the class, this person stood up and walked out of the room. After the class, Rav Noach caught up with him and asked why he left all of a sudden. The man replied that he saw that he was starting to become convinced and he realized that if he came to the conclusion that Hashem exists and the Torah is true then it would mean changing his entire life. He did not want to do that so he forced himself to leave the class “before it was too late.”
As sad and as extreme as this story seems, we should look at our own lives and ask ourselves whether we too, on our level, are doing exactly the same thing.
 Ksav Sofer, Shemos 10:26.
 It is clear, though, that if they would have devoted more energy to Moshe’s words, they would have been convinced (Rav Zev Leff).
 At the same time, we must be weary of the evil inclination’s attempts to push us too fast. Each person must take gradual and thought-out steps how, where and when to grow; but never place a permanent block in the way of coming closer to Hashem.