In an article published in 2013, author and blogger Mark Manson pointed out the importance of passion in whatever you do. This is especially true for the founders of startups – they have to be passionate enough about their vision of changing the world to work through being hungry, overworked, underslept, and broke for years before the vision becomes reality (and a source of hopefully substantial income). Think of how much time and effort founders dedicate to their products, and then think of how hard and painful it must be for a founder to leave the company he or she created. After all, it’s the result of a long and laborious process and a lot of sacrifices – calling it quits and cutting all ties to it is probably one of the most painful things they can do. Yet it happens more often than you think.

Last year, both Instagram founders quit Facebook. Kevin Systrom and Mike Krieger founded the company in 2010, and they dedicated a lot of time and effort to the project. The idea caught with the public, becoming a major hit and ultimately being engulfed by the big blue social network, Facebook, in 2012, for $1 billion in cash and stocks. Unfortunately, in the years that have passed ever since, they have seen their project go in a direction that they didn’t like – and last year, they have finally reached a point where they called it quits. In the announcement of their departure, the two co-founders of the service promised to channel their creativity to other projects while continuing to watch Instagram (and Facebook) develop.

Systrom and Krieger are not the first founders to leave their projects behind. In 2015, Mark Pincus relinquished control of the company he created – mobile and social gaming giant Zynga. His reasons for stepping down were valid, no matter how painful it must have been for him to leave: he said he considered himself to be a good entrepreneur but not a good chief executive managing large groups of people, and this was a good enough reason for him to take a step back. In a similar move, Groupon founder Andrew Mason also left the company he created in 2013, blaming himself for the results the business has posted in the months prior to his departure.

Leaving the company they created is painful for the founders but it can be harmful to the companies as well. In the vast majority of cases, the founder or the synergy of the co-founders is the creative spark behind a service – losing them may kill the innovative nature of the company and completely change the direction in which it is headed. Thus, holding on to their founders can be a vital decision for online services and businesses, in general.