Rose Quartz is another of those "must have" stones for metaphysical work. It is a beautiful rose colored quartz (hence the name, go figure), and is readily available in many different forms.
Rose quartz is said to be a calming stone, and one that can change the flow of negative energy to positive. It is a soothing stone, even when you just hold it. Rose Quartz is said to act as a balancing stone for the first four chakras, and perhaps that is why it is such a "feel good" stone.
The pink color of rose quartz is often associated with feelings of love, especially unconditional love. The more love, the less stress. Seems pretty happy to me :-)
Rose quartz is also said to be a stone useful to those making the transition from life to death. Hopefully none of us will have the opportunity to test that theory.
If you need a stone to bolster low self esteem, rose quartz is your rock. Its energies are said to balance out the emotions, and help us accept ourselves as we are.