A questioner asks: How do you maintain sincerity in good deeds without other worldly things motivating you as well?
First and foremost we should monitor our heart to make sure that it is pure. Then we should make dua to Allah. Prophet Muhammad (PBUH) told us to seek refuge in Allah from any type of showing off.
It is very important to make sure that you have a lot of private good deeds as well. The majority of your good deeds should be private. Make sure your voluntary prayers are done privately. Give charity in private.
If you help a good friend don’t post it all over social media saying that you have done so. This should be done for the sake of Allah not for you to show off in front of others.
All of these tips will make your good deeds more and more sincere.