Parashat Terumah begins with Hashem commanding that donations should be collected for the construction of the Mishkan . He tells Moshe, מאת כל איש אשר ידבנו לבו תקחו את תרומתי – the donations should be taken "from every person whose heart stirs him." Hashem wanted the donations to be received only from specific kinds of people – from those אשר ידבנו לבו , who were driven to donate by sincere motivations. Many centuries later, when the Bet Ha'mikdash was to be built, we find a similar emphasis on pristine sincerity. The pasuk (Divrei Hayamim I 22:8) says that Hashem did not allow David Ha'melech to build the Bet Ha'mikdash because he fought many wars, during which he killed many people. The Mikdash was built by his son, Shlomo, during whose reign there was peace, and who thus never fought any wars. The Malbim offers a fascinating explanation for why David's fighting wars disqualified him from building the Bet Ha'mikdash . He writes that David knew that the Bet Ha'mikdash could be built only in a time of peace, when no more wars would be fought. Therefore, if he would have built the Bet Ha'mikdash , he might have been motivated to do so by a desire to once and for all end the wars. He might have thought that the presence of the Bet Ha'mikdash would itself bring an end to the wars – and this would be part of the reason why he would want to build it. When Shlomo built the Bet Ha'mikdash , he had no agenda. His intentions were purely לשם שמיים , for Hashem's sake. If David would have built it, his motives would not have been entirely agenda-free. There would have been a tinge of self-interest involved. Whenever we embark on any significant project, the most important thing we need to help us succeed, to help us overcome the challenges that will invariably stand in our way, is לשם שמיים – sincerity, pure motivations, a genuine drive to do something valuable and meaningful for Hashem. So many people underperform and underachieve. All the accumulated baggage of the past – all their disappointments, failures and painful experiences – discourage them and hold them back. This baggage is deflating, so people don't proceed with the energy, determination, passion and conviction that they need to succeed. The key to solving this problem – which plagues so many people, and which prevents so many people from building and achieving – is לשם שמיים . A person starting a business should think about all the good he could do with a successful business – how he can help people, provide jobs, make a קידוש ה' through his interaction with different kinds of people, support his family, give tzedakah , and donate to religious institutions. A person who is looking for a marriage partner should be driven by a genuine desire to build a beautiful Torah home, a home of hesed , a home where children will be raised according to our Torah values. This is true of any ambitious project that a person wishes to start. The emotional fuel he needs to succeed is לשם שמיים – a passionate desire to do what Hashem brought him into the world to do, to accomplish what Hashem brought him into the world to accomplish, to contribute what Hashem brought him into the world to contribute. If we bring this feeling with us, then we become unstoppable, and no amount of baggage can hold us back from succeeding.