Do not attach to ANYTHING, the very nature of attachment in itself brings suffering, even attachment to serenity or insight.
Otherwise, one becomes a run-of-the-mill person all over again, you attain a meditation state - you're happy, you don't get it, you're stressed, worried, or doubtful, ignorant to the fact that all things arise due to its causes and conditions, not aware that in the undercurrent of all this - the defilement are working full force and indeed laughing at you.
If you have 'certain experiences' on retreat, just better leave those experiences back at the meditation center and forget about it- just see what insight follows you when you get back to lay life.
Otherwise, one would be basking in one's
self proclaimed attainments and then one is really stuck.
This is what I meant by 'spiritual materialism', I'm sorry if I sound vague as my language skills and Dhamma practice is limited.
Indeed, we should aspire to the Ariyan attainments, but perhaps, with the right attitude.
Venerable U Tejaniya has an important message, even if it is 'Dhamma-lite'.
with metta