There is no religious reason for a saved Jewish person to be keeping the old covenant rituals. They are free to observe certain customs for social reasons, e.g., the eating of certain foods, but those customs have no religious significance under the new covenant for either Jews or gentiles.
They also need to be careful to appreciate that certain customs cannot be kept in the fashion of the old covenant in any appropriate form, e.g., the sacrifice of animals for the "remission" of sin. This poits out one obvious difficulty with trying to observe the old covenant feats days. They were all intimately tied to the temple sacrifices, and once the temple was destroyed and the sacrifices ended, the feast could not be properly conducted. The Jewish feast customs today (Passover, etc) are based on post-exile rabbinic traditions. Jewish believers should be very wary about following such traditions and customs.
Amen. Paul calls them 'weak and beggarly elements' (Gal.4:9)
Attendance at the Temple was a special event.
In the meantime,
Luke 4:14-30 14 And Jesus returned in the power of the Spirit into Galilee: and there went out a fame of him through all the region round about. 15 And he taught in their synagogues, being glorified of all. 16 And he came to Nazareth, where he had been brought up: and, as his custom was, he went into the synagogue on the sabbath day, and stood up for to read. 17