Hi Hershi,
pretty impressive that u chose a middah and u wanna work on it.
Like with all middos, we have to slowly work on it, piece by piece till we get better and better. Running 2 the opposite extreme is dangerous and will in all likelhoods end in a flop.
Choose something small to start working on. This could be 1 person who u find hard to give to and once a day give something to him. Or this could be 1 act u find hard to do (such as let a car go b4 u u) or whatevr and do it once a day. As you start training urself more and more and u feel the barriers of selfishness falling a bit more each day, u cud add on something else 2 “practice”. Eventually, u will find it starting 2 become more natural 2 u. Remember that breaking middos is hard and may take a long time- (even a lifetime!) but with hard work, u’ll get there Iyh.
Good Luck!