Destiny can be changed.
Hukam is ALL his.
If destiny couldn't be changed, the what would be the point of sikhi ?
Destiny is only pre-ordained according to your current state of inner awareness and consciousness. Basically, if you continue going the path and with state of mind you are at at any given time, then destiny dictates UNDER the command of Hukam.
Probably wondering, how do you change it ??
By raising your consciousness.
This is only done if you make the effort to learn about your soul/consciousness.
This is what a TRUE SIKH is supposed to be a learner about.
To learn how to realize God by climbing up the spiritual ladder. This ladder has rungs which are all out of the boundaries from Kaal.
Only AKAAL can put his hand down to help and guide you up. But you have to make that effort to start learning and climbing.
There is ONLY ONE method, I know...........NAAM SIMRAN !
Only Naam simran/meditation can take your inner 'antar ghath' to be outside the boundaries or influences of maya and thoughts.
Remember- ALL thoughts and deeds are MAYA.
Maya has 3 modes or gunas whichcan all be classed as Satogun, tamogun and ragogun.
Of these the higher good actions and thoughts are Satogun or satvic.
BUT,BUT........BUT...
Just doing Good deeds/being righteous/good thoughts can NOT help you climb that ladder !
WHY ??
Because, the good satogun stuff is STILL MAYA.
It may make you feel like you are doing the right thing, but you are only viewing on the surface and not getting into the esoteric layers of sikhi.
ONLY meditation can help you control your MIND in order to get out of 3 gunas of maya.
When you achieve the meditative state outside 3 gunas, which will be without any thoughts, then there is only You and GOD. Nothing else.
In fact, you should realize there is ONLY HIM
This is the Goal.
This is the merging.
This is what you have to work at to maintain, so that it becomes a continuous state of sehaj.
Then, you reach territory of gurmukh and jivan mukht.
Then you pass all the planes/realms of mind and reach the True abode of Sachkhand.
As for REINCARNATION and TRANSMIGRATION.
Gurbani doesn't tell us that it doesn't exist.
It tells us that ONCE, you reach that ultimate state of being with the TRUE SAT in sackhand status, then for you there will be NO reincarnation, No karma, No past negative affects on present....
But for all the others mingling on the lower levels and states of consciousness, they will continue to revolve in the circles of birth/death, karma, destiny, free will-playground (recess) time......and repeat.....repeat......