All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Patience occurs either when something bad takes place or when one misses something that he loves and desires. One is rewarded for patience in the two cases when he does so sincerely for the Sake of Allaah The Almighty and seeks His reward. Refraining from having more than one wife in order not to hurt her feelings or to avoid the consequent problems is included in the second type of patience. One is rewarded for this when he remains patient for the Sake of Allaah and seeks His reward.
The questioner should know that the human soul usually aspires to what it is does not have. If you married a second wife, you would still desire others, and so on.
Allaah Knows best.