Whenever we speak of anything spiritual, we can connect it to our inner soul. Some others may connect it to the word God. However, this is a very complicated thing and this sense can only be attained through practical experience. Spirituality is nothing but the feeling of the existence of God in our soul. God is great. He is omnipotent and omnipresent. His presence is in every human being and in every corner of the world. He is big, but He is so small that His every little bit, is in every corner of the world.
Go back to those school days when you studied Biology as a subject. During the practical classes, many a times you may have watched unknown things happening under the microscope. These things are the ones that you had not known until then. It is like a discovery of a new civilization of microorganisms. We all know that a microscope magnifies a thing 200 to 400 times, than it is. Moreover, you will be surprised to know that God is even smaller than that, though not yet proved by the scientists.
The universe has so many large things that are too small to see. This is again a controversial topic, yet there is truth to it. For instance, humans can hear a sound range of 20 Hz to 20,000 Hz. Nor can they hear anything below 20 Hz, called infrasonic sound; neither can they hear anything above 20,000 Hz, called ultrasonic sound. Similarly, humans cannot see anything that is too small to see, or too large to see. Like hearing range, they have a sight range too. Therefore, God is so great that he is too small to see.
The definition of God and belief of His existence may vary from one individual to the other. Some people believe in God, while others do not believe because they cannot see. Every individual has his or her own point of reason. However, it is proved that whether or not people believe in the existence of God, a spiritual force works on this universe and everything happens on the work we do. If we do any good work, we get good results, and if we do anything bad, we get bad results. It is like a divine feeling that brings the positive feelings within you in times of fear, mishap, or any ill conditions. Thus, the real existence of God or this spiritual force lies in your soul.