Yes, it is possible to give your plants too much water. Overwatering can cause less oxygen to go into the roots of the plant and the soil which can lead to root rot. Proper aeration and drainage in your soil is crucial for plant survival, otherwise your plant will die or have slow, stunted growth. Use your fingers to check the soil for dampness about 2 inches deeper than the surface, if it already feels wet do not add more water. If you don't want to get your fingers dirty every time, use a soil tester instead to make sure you are giving your plant enough water without overdoing it.