This is quite an overwhelming experience reading the first Daf. Each person walks their own way, and each goes to bed and wakes at their own time. Some go to bed after working the whole night. Should they recite the evening shema when they lie down or when it is nighttime ? If the recital of the shema prayer is based on customary times, then it does not account for the individual’s intention to connect to Hashem, or correlate to the individual’s need to reset the internal clock ?
As opposed to much of western thought, in Am Yisrael we see importance in being one united communal nation. Accordingly, if we want one objective and national Torah, that Torah obviously has to refer to the norm and common behavior, and as is explained in the Oral Tradition. On the other hand, we're not communists and the halacha leaves a lot of room for the individual's needs as well, for we each have a unique spark of God which should not only be tolerated, but encouraged. Accordingly, we say shma at night, when most people go to sleep, but if one works at night, he can say it over about a 12 hour (!) period (extremely flexible), when it works for him. The morning shma has about 3 hours when most people wake up (that being said, again we are a community, so if possible, it's better to say with everyone at shul, as is the case at night, as well). In addition, you can say additional "shmas" whenever you feel like it throughout the day, but there has to be a minimal basic framework for all! May I add that if this type of study/thinking isn't for you, I suggest you leave gmara for a later stage in your Torah-study development and focus on more basic and applicable issues, such as Jewish thought and philosphy, hassidut, Tanach etc. which are more suited to most people.