When God created Himself, He created Himself in two aspects: the Infinite and the finite. When you think of the finite, you think of form, and when you think of the Infinite, you feel that there is no form. However, inside the finite is the message of the Infinite; in the finite is first the revelation and then the manifestation of the Infinite. The finite is necessary because it is through the finite that the Infinite plays its role in the cosmic rhythm here on earth. At the same time, the Infinite is necessary because it is in the Infinite that the finite has its eternal shelter. There it finds protection and perfection.
The Formless is necessary to realise the Highest, the Ultimate, the Infinite; and the form is necessary to reveal and manifest the Highest and the inmost in an intimate way. That which is infinite in consciousness can be seen only in the formless form. Again, it can house itself in form. That is why the heart can hold Infinity inside it. When you enter into the subtle physical, it is all formless when you enter into the physical, it is all form.
If you meditate in order to achieve some thing in a most tangible and intimate way, it is helpful to approach the Supreme in the form of the Mother, the Mother Divine. But if you want to experience something in abstract form, in the form of energy or ether, then you will approach an endless, formless form.