Glory to God that He has put such joy in your heart! Of course there will be hard times and perhaps you will not always feel so elated, but you already know that. It is normal and human to experience grief and sadness as well as happiness. Just look at the Psalms. And even Jesus wept over Lazarus. But I think Jesus was also always joyful, even on the Cross. Because true joy and gladness and the peace that doth pass all understanding is a gift of God that cannot be taken away by external circumstances. You received this gift when you were chrismated, and you should treasure it. Again, Glory to God! Of course, it is easy to fall into the trap of letting our relationship with God be defined by our transient emotions. If you had experienced negative emotions since converting, conversion still would be right; we know this because Orthodoxy is objectively true, regardless of how we feel. Be faithful to God no matter what - that is what matters. IT seems to me we can also lose our joy if we forget God in sinful pride and self-sufficiency. But we can always return to Him in repentance and He will be running out to meet us. If we turn to Him in faith and repentance He is always ready to fill our hearts with supernatural joy and gladness.
I am very happy for you that you are experiencing joy since your conversion. Thanks be to God!