I think the most important thing is the spirit in which you do things. If you're doing it because you feel it brings honour to God to keep a sabbath for whatever reason (maybe you put aside a day to be with God in prayer and in the scriptures or spend time in His creation etc.) then there's nothing wrong with that and, for you, the sabbath is still very real and valid. As followers of Christ in the new covanent, we aren't bound by old testament laws and traditions (including the sabbath), rather we have been saved by grace and we won't be measured against the law. That said, a lot of today's western moral code is derived from teaching across the Bible, including the law. The law also serves to show us God's ultimate standard for humanity and how much the Isrealites had to do to keep themselves right with God. It shows us how helpless we are without God's intervention and that it is only because of Jesus that we can be made right with God.
If you are keeping the sabbath because you see it as a hard and fast rule that can't be broken or others are making you feel that to be a genuine Christian you must keep a sabbath day then I would question the motives there. Keeping a tradition in place for no other reason than it makes you feel superior to those who don't, or so that you will look good next to someone who does isn't going to serve to honour God, only those who would impress this tradition upon others. Christians in the early church were advised by Paul in regards to different festivals, what they do or don't eat and drink doesn't matter (see Colossians 2:16-23). v23 says: "Such regulations indeed have an appearance of wisdom, with their self-imposed worship, their false humility and their harsh treatment of the body, but they lack any value in restraining sensual indulgence."
Paul also writes to the Corinthian church about a similar matter (1 Cor 10:23-33). Although this is directly about meat that has been used as a sacrifice, the logic still applies. You are free to choose and your salvation is not hinged on whether or not you keep the sabbath, or even on what day you observe it. As v 31 says: "whatever you do, do it all for the glory of God."