Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
One of the obvious sings of the acceptance of acts of worship is when Allah the Almighty guides us to perform another act of obedience. Another sign of acceptance is the byproduct of thinking well of Allah.
Answering your question, Dar Al-Ifta Al-Misriyyah, states:
The issue of acceptance of acts of worship has occupied the mind of renowned Muslim scholars along centuries and they tracked some signs which help us in realizing if our acts of worship were accepted by Allah the Almighty.
Sa`id Ibn al-Musayyab tackled this issue and stated that one of the obvious sings of the acceptance of acts of worship is when Allah the Almighty guides us to perform another act of obedience following the act of obedience which was performed.
For example, If a person was blessed with praying the Noon Prayer and then he was guided to perform the Afternoon Prayer, it is a sign that the noon prayer was accepted as Allah has guided him/her to perform another act of obedience following the first one.
Another sign of acceptance is the byproduct of thinking well of Allah (hus adhzan b-Allah) as Allah the Almighty said in his Qudsi Hadith, “I am as my servant think of Me”.
Therefore, Muslims ought to think well of Allah the Almighty and to believe that Allah is All-Merciful and Most Gracious. Thus, He out of His infinite mercy, will accept our good deeds and forgive our bad ones.
Almighty Allah knows best.
Source: http://www.dar-alifta.org/Foreign/ViewFatwa.aspx?ID=10507