Therapy can be helpful in a variety of situations and is frequently used to work on issues both large and small. In fact, sometimes small issues can become larger issues over time, so from my perspective it's never too early to work on an issue that is a concern. Therapy can be a good place to develop goals, and to create the plans to meet those goals. Therapy is also frequently sought out to improve a person's mood, sleep, and stress levels.
Couples frequently seek out therapy to address issues centering on communication, trust, and growing apart. Couples therapy can also help to further strengthen relationships that may already be strong, and can benefit couples preparing for relationship milestones (or adjusting to them).