The Be’er disappeared when Miriam died
For almost 40 years, as the Jews travelled in the desert, their source of water was the Be’er: a large rock that provided the water they needed to survive. Keeping in mind that the Jewish nation consisted of about 3 million people, and they took many animals with them when they went out of Mitzraim; they required millions of gallons of water each day.  The Be’er provided all they needed and more.  When Miriam died, the rock disappeared, and the Klal Yisroel recognized that their survival was in jeopardy. HASHEM told Moshe Rabbeinu, to go out into the desert, speak to the rock and bring it back. When Moshe and Aharon went to seek the rock, they spoke to it, and received no response. Moshe then assumed that just as it was necessary to hit the rock when the Jews first went out into the desert, so too now. When he hit the rock it began pouring forth water.

Later, HASHEM told Moshe and Aaron that they had erred. HASHEM told them to speak to the rock, and it was through the power of speech that the miracle was to come about. On some level they were lacking in their trust in HASHEM, and this caused them to miscalculate. Had they been more complete in their trust, they would have used words alone, and the rock would have provided the water.

Rashi tells us, that because of this mistake a great lesson was lost to the Jewish People. Had Moshe only spoken to the rock, the Jews would have said to themselves: “A rock doesn’t require sustenance, yet it listens to the word of HASHEM; surely, we, who rely on HASHEM for parnasa must listen to Him”. However, since Moshe hit the rock instead of speaking to it, that lesson was lost.

Rashi seems to be saying that if Moshe had spoken to the rock then the Jewish people would have increased their level of serving HASHEM.  They would have realized that their livelihood was dependent upon their doing Mitzvahs, and this would have added focus and precision in the way that they fulfilled their mitzvahs
 
 
The  reward for doing the Mitzvahs isn’t in this world 
Reward for Mitzvahs isn’t in this world
There are two problems with understanding this Rashi. 1. Is that the Gemerah tells us that the reward for Mitzvahs is not in this world.  While it is true that HASHEM rewards every good a person does, the place of that reward is in the world to come. In fact, it is considered a curse to use up your payment in this world- something that is reserved for wicked people.

The second problem with this Rash is that any motivational system must be tailored to fit the audience. The people of this generation received the Torah on Har Sinai. They spent almost forty years, eating Mon, being surrounded by the clouds of glory, completely immersed in Torah – They were on the highest madregah of any generation in history. How could they be  motivated by something so mundane as earning their daily bread? This would sound like a weak motivation for this group. 

Obstacles that prevent us from serving HASHEM
The answer to this question is based on the  Rambam in Hilchos Tshuvah Perek 9 where he explains: even though we don’t receive reward for doing Mitzvahs in this world, if a person keep the Torah properly, then HASHEM will remove all of the obstacles that normally prevent a person from keeping the mitzvahs. For instance, sickness, war, poverty and hunger will prevent a person from learning or fulfilling the Mitzvahs. If a person is happy and dedicates himself to keeping the Torah, HASHEM will shower him with all of the requirements to better serve Him, including, peace, tranquility, well being, health, sustenance…and all else that a person needs to follow the Torah. 

The Rambam is telling us that since HASHEM created the world in order to have man follow the Torah, if a person uses the world properly, then HASHEM allows that person to have his needs met in this world without strain, in order that he can thereby better serve HASHEM.

HASHEM was telling Moshe and Aharon that this lesson would have greatly affected the generation of the desert, and it was lost. Had the people seen Moshe speak to the rock, and the rock obeyed HASHEM’s command, they would have been moved to a powerful realization: the rock doesn’t have needs, yet it listens to HASHEM – how much more so we who have so many needs…. Who provides for our needs? HASHEM. And HASHEM has promised that if we follow in his ways He will remove all obstacles from our path, and if we don’t listen…

That was a lesson that would have affected even this generation- because their very survival depended on it. While a person may have many lofty motives, one of the strongest drives in man is self preservation. Had they come to a more clear recognition that their very survival is dependent upon keeping the Torah- it would have changed even their appreciation—and it was a lesson lost.

Earning a living isn’t easy
This concept: that if we use our life properly, HASHEM will take care of our needs, can be a great source of motivation. The reality is that earning a living isn’t easy. Market economies rise and fall- entire industries come and go, careers that are in high demand in one decade are outsourced and send over seas the next -- financial security in an ever changing world is fragile at best.

While our main motivation to keep the Torah is because HASHEM commanded us to do it for our benefit in the World to Come – the reality is that we live in this world. We have bills to pay, children to put through school, and many, many financial obligations. Knowing that if I dedicate myself to passionately keep the Torah, HASHEM will remove those obstacles that stand in my way, can be a great impetus to growth.

Not to say life will be a bed of roses, there will still be Nisyonos, life tests and different settings that we need for various reasons. However the basic starting position that HASHEM will take care of my needs so that I can better serve Him, can aid a person in focusing on their true purpose in this world, and allow them a much greater degree of success in all of their endeavors.