There's a lot of passionate energy swirling around you two during this three-week period, and you should certainly put it to good use. This kind of energy requires focus and direction, so don't let it go to waste! First off, this is the kind of phase that's perfect for new beginnings.
Start a new, active project together, like building something at home, joining a gym or training for a marathon. Whatever you set your minds to now has a great chance of meeting with success, so choose something that really means a lot to both of you. Don't shy away from long-term projects, either; this is the beginning of a new phase of your relationship, and you should be quite conscious in shaping and determining the next couple of years ahead of you. Again, keep it active! You've got extra energy that needs to be expelled now; if you don't, it could start coming out in other ways, such as arguments and confrontations. If you notice yourself getting a bit irritable, go for a jog and ask your sweetie to join you. That's the best way to turn a mountain back into a molehill now, and to properly channel your energies so that they don't devolve into needless aggression.