How can one return to nearness to Allah and contentment after inclining towards worldly matters and feeling anxiety and distress?

The cure for complaint is repentance to Allah and seeking His forgiveness, and returning to what you were upon and even better. For Allah does not change the condition of a servant unless the servant changes his own condition, as stated in His saying, the Most High: "Indeed, Allah will not change the condition of a people until they change what is in themselves." So, the rectification of souls is the basis for the moderation of conditions, and every affliction in religion or in this world is due to the sins of the servant, as He, the Most High, said: "And whatever strikes you of disaster - it is because of what your hands have earned." So, seek help from Allah and resume your state with Him, and know that Allah is too generous to turn away His servant if he returns to Him. So, be for Allah as He wishes, and He will be for you more than you wish.