Don't say "I have to" or "I wish I could" those are negative mental patterns that make you feel negatively towards your goals.
Say "I want to" "I will" "I can". Positive mental attitudes will change how you feel about doing anything.
If you want happiness for an hour, take a nap. If you want happiness for a day, go fishing. If you want happiness for a year, inherit a fortune. If you want happiness for a lifetime, help someone else.