Get walking together! You could look at local trails and public footpaths, this is a lovely way to explore nature locally and can be extremely romantic. In summer, add a few bits of food and drink and you've already got yourself a picnic! So dreamy!
Next, look at doing some kind of sport together. If you're gym members then why not go together and if you're always busy then this is a great time to catch up on a little bit of chit chat before you go to work. If the gym isn't for you then there is always something a little different such as indoor rock climbing which is a great team building exercise and bonding exercise, so this is perhaps one for those in a newer relationship. Canoeing, sailing, swimming and badminton are all other forms of sport that release endorphins and make you feel confident and energized. You can always have a good laugh doing these activities and there's always good memories to be made from it. You never know, perhaps you'll find something you really enjoy doing and then you're well on the way to adopting a long term healthy lifestyle as well as a more comfortable relationship.
Of course eating out and good food is a priority so keep that fresh too and try new places to eat around town, so you're not limiting yourself. Variety is the spice of life and if you're stuck in a slump then your relationship can easily become stale and mundane. Try new places and just see what you find. It doesn't have to be far, try local; you may be surprised! Give yourself time to relax too because running around and getting caught up in manic life can be unhealthy and you may end up feeling more sluggish. Plan ahead, instead of date night at the cinema, make your date night an evening at a yoga class together or an early evening cycle, ready for a nice long cozy bath upon your return. There's never any need to feel sluggish in your relationship again!