What adhkār do you recite in ṣalāh? Are they always the same adhkār? Do you tend to repeat the ones you memorised when you first learnt how to pray?
To avoid monotony in your ṣalāh, try to memorise and pray the different adhkār and duʿās within your ṣalāh (particularly in voluntary prayers). This will increase your khushūʿ, help you to taste the sweetness of ṣalāh, and encourage you to reflect on the words you are saying. The adhkār of the Prophet ﷺ are very powerful and comprehensive. It would be a huge loss to pass a lifetime without having ever invoked Allah (ʿazza wa jall) with these adhkār in your ṣalāh.
Try to alternate the sūrahs you recite during ṣalāh. This will mean making an effort to memorise more of the Qur’ān. Also, make a conscious decision before the ṣalāh to choose which sūrah/dhikr/duʿā’ you will pray. By the will of Allah (ʿazza wa jall), this will also help to increase your khushūʿ.
Reflect on the meanings of the various adhkār
Once you have memorised the adhkār, try to reflect on their meanings in each ṣalāh. Your ṣalāh will become lengthier, and the connection between your heart and Allah (ʿazza wa jall) will deepen.
Three Benefits of Varying Your Adhkār
1. Follow the Sunnah more comprehensively.
2. It is a means of reviving the (abandoned adhkār of the) Sunnah.
3. It becomes easier to reflect on the meanings, in comparison to reading out of habit.