The most excellent fast after Ramadan is God's month. al-Muharram, and the most excellent prayer after what is prescribed is prayer during the night.  

قَالَ رَسُولُ اللَّهِ ﷺ أَفْضَلُ الصِّيَامِ بَعْدَ رَمَضَانَ شَهْرُ اللَّهِ الْمُحَرَّمُ وَأَفْضَلُ الصَّلاَةِ بَعْدَ الْفَرِيضَةِ صَلاَةُ اللَّيْلِ  

The Prophet ﷺ never fasted in any month more than in the month of Sha'ban.

He used to say, "Do those deeds which you can do easily, as Allah will not get tired (of giving rewards) till you get bored and tired (of performing religious deeds)." The most beloved prayer to the Prophet ﷺ was the one that was done regularly (throughout the life) even if it were little. And whenever the Prophet ﷺ offered a prayer he used to offer it regularly.  

لَمْ يَكُنِ النَّبِيُّ ﷺ يَصُومُ شَهْرًا أَكْثَرَ مِنْ شَعْبَانَ فَإِنَّهُ كَانَ يَصُومُ شَعْبَانَ كُلَّهُ

وَكَانَ يَقُولُ خُذُوا مِنَ الْعَمَلِ مَا تُطِيقُونَ فَإِنَّ اللَّهَ لاَ يَمَلُّ حَتَّى تَمَلُّوا وَأَحَبُّ الصَّلاَةِ إِلَى النَّبِيِّ ﷺ مَا دُووِمَ عَلَيْهِ وَإِنْ قَلَّتْ وَكَانَ إِذَا صَلَّى صَلاَةً دَاوَمَ عَلَيْهَا  

He (al-Bāhilī) came to the Messenger of Allah ﷺ, then went away and came back to him after a year, and his condition and appearance had changed. He said, “O Messenger of Allah, do you not recognize me?” He said, “Who are you?” He said, “I am the al-Bāhilī who came to you last year.” He said, “What has changed you, when you used to be of good appearance?” He said, “I have not eaten any food except at night since I left you.” The Messenger of Allah ﷺ said, “Why have you tortured yourself?”

Then he said, “Fast the month of patience (i.e. Ramaḍān), and one day from every month.” He said, “Increase it for me, for I have strength.” He said, “Fast two days.” He said, “Increase it for me.” He said, “Fast three days.” He said, “Increase it for me.” He said, “Fast during the sacred months and leave off; fast during the sacred months and leave off; fast during the sacred months and leave off.” And he gestured with his three fingers, drawing them together and then releasing them.  

أَنَّهُ أَتَى رَسُولَ اللَّهِ ﷺ ثُمَّ انْطَلَقَ فَأَتَاهُ بَعْدَ سَنَةٍ وَقَدْ تَغَيَّرَتْ حَالَتُهُ وَهَيْئَتُهُ فَقَالَ: يَا رَسُولَ اللَّهِ أَمَا تَعْرِفُنِي؟ قَالَ: «وَمَنْ أَنْتَ؟» قَالَ: أَنَا الْبَاهِلِيُّ الَّذِي جِئْتُكَ عَامَ الأَوَّلِ۔ قَالَ: «فَمَا غَيَّرَكَ وَقَدْ كُنْتَ حَسَنَ الْهَيْئَةِ؟» قَالَ: مَا أَكَلْتُ طَعَامًا إِلاَّ بِلَيْلٍ مُنْذُ فَارَقْتُكَ۔ فَقَالَ رَسُولُ اللَّهِ ﷺ: «لِمَ عَذَّبْتَ نَفْسَكَ؟»

ثُمَّ قَالَ: «صُمْ شَهْرَ الصَّبْرِ، وَيَوْمًا مِنْ كُلِّ شَهْرٍ۔» قَالَ: زِدْنِي فَإِنَّ بِي قُوَّةً۔ قَالَ: «صُمْ يَوْمَيْنِ۔» قَالَ: زِدْنِي۔ قَالَ: «صُمْ ثَلاَثَةَ أَيَّامٍ۔» قَالَ: زِدْنِي۔ قَالَ: «صُمْ مِنَ الْحُرُمِ وَاتْرُكْ، صُمْ مِنَ الْحُرُمِ وَاتْرُكْ، صُمْ مِنَ الْحُرُمِ وَاتْرُكْ۔» وَقَالَ بِأَصَابِعِهِ الثَّلاَثَةِ فَضَمَّهَا ثُمَّ أَرْسَلَهَا