What you do together is life. What you think about doing together is imagination. Bringing those to ideas together into all the things you like to do, anticipate doing in the near future, and aspire to do as part of your long-term goals... All of this is part of building and nurturing a relationship for the future.
We put time into the relationship, we want results. We invest our heart and soul in a person, we hope they will return the gift. But people are funny.
When contemplating a long-term relationship, unaddressed issues will not get fixed on their own. They will fester until one partner breaks either with anger or acting out. And if the issue has been around for more than 6-months you owe it to yourself and your partner to address it head-on.