My 40s and 50s were not the 'best days of my life'. I was working full time to fund both DDs through University and missing them a lot. We could not visit them (or take other holidays because I was also 'caring' for My DM, MIL, FIL Aunt and Aunt IL who were in and out of hospital over several years until they all died within a year of each other and coping with my own health problems - an endless menopause with severe bleeding, restless leg syndrome and clinical depression.
I did manage to complete the 2 year Counselling diploma but 2 years later was made redundant at 52 when the local Council slashed our funding. I managed to get a couple of low paid clerical jobs to keep us solvent until I reached retirement age.
But my 60s were a wonderful decade. Free of caring responsibilities, I completed 3 modules at Uni (just for fun and to prove I could do it, crossed Canada on a shoe string with DH and elder DD, enjoyed a Mediterranean cruise for our Ruby Wedding and other wonderful holidays abroad, welcomed both DDs when they moved back to live near us and soon presented us with 1, 2, 3 DGC in rapid succession, leading to a busy new life of childminding, voluntary work and political activity.
All change again in my 70s with DH's illness which means a very quiet but stressful life mainly at home. No point in having regrets, it is just the way the cookie crumbles and we have to make the best we can of each phase and seize whatever chances for happiness that come along.