Do not dwell in the bad things/bad moments you had with him/her.

Remember the good, even if it's bittersweet at best; it's a hell of a lot better than the alternative.

Try not to commit the same mistakes that they did, let him/her work as an example for you in the good and the bad sense.

Be happy, it's what your parents wanted after all. If you're not satisfied with what you have, work harder towards your goals.

There's not guarantee that you will achieve them, but if you do nothing, nothing happens.