It is said that we should never lose hope in Allah and that we should always pray for that which we seek as Imam Ali (a.s) has said that impossibility and possibility are merely concepts of our mind; for Allah nothing is impossible.
But sometimes you pray so much for something that you want yet you see it slipping away but you still continue to explain to yourself how Allah is Qaadir and the one who fulfils hopes, and how the Prophet and his household never let anyone go empty handed if asked for anything by giving their waseela. You explain yourself all this and you continue to pray with full hope and belief of qabooliat since when asking for something you should have belief on qabooliat.
But eventually that thing slips away from you. Since Allah is all knowing so you don't complain to Him.
But your hopes have been shattered, your heart is broken and all those months of endless prayers while crying didn't seem to work.
Allah always does what's best and again He's Qaadir.
But what should one hope and pray for now?
Hope and pray with full belief that you'd still get back that thing even though it has clearly completely slipped away, but Allah is Qaadir.
Or just hope and pray to Allah that He do whatever's best for you whether you get that thing or not, basically just leaving everything to Him.
I know it's best to leave it to Him but if only that happens which Allah wills then what is the point of dua?
Dua changes fate. May be it's written that you ask for it then it would be given to you.
Believing on this we make dua and that is what I did but is there any limit to hope on Allah? Because when it doesn't happen, you're left broken and saddened.
like when I pray for something I do it with full belief and so I tend to make future scenarios in my mind so is that which causes so much sadness?
If so, then what is the limit to hope or the right way to hope?
One should stick to the present in order to be happy but prayers and hope is always for the future, so how to hope if not think about the future?
My present is sad and I don't know what to think, pray or hope
I know Allah is all knowing and does everything for the best and I believe that He will do the best for me in the future as well.
Alhumdulillah for everything and I don't have any complains from Allah but I'm still in a confused state of mind with regards to what to pray and hope.
I hope this confusion does not upset Allah and become a reason for delay or rejection of qabooliat.
I take over guilt very easily and as much as I feel comfortable in letting my heart out and praying to Allah, I'm afraid of making Him upset because of all these confusions.
Any advice would be helpful.

Indeed Allah is Qadir and the Quran always reminds us not to give up hope irrespective of how long it takes to receive the good news. Although sometimes it can be difficult for insaan to keep waiting for long without complaining. The holy prophet explained reasons as to why we think our Duas are delayed sometimes:
1. May be the dua is used to forgive our sins instead of been granted what we are asking for
2. Allah is happy to hear your voice and that eventually He grant you your wish. Many stop making dua once their wishes are granted
3. May be whatever you are asking is not good for you and that Allah replaces it with something else. Hence good things sometimes happen in our lives without us asking for it

I know it can be difficult waiting but remained positive and keep insisting, the door will be opened insha Allah